Patent Description:
D4 wood adhesives require specific durability as they are used in interior areas with frequent long-term exposure to running or condensed water and/or exterior areas exposed to weather. Suitable adhesives are not only excellent in dry adhesive performance, but also in secondary performance such as water-resistant adhesion, boiling-water-resistant adhesion, and heat-resistant adhesion. Conventional water-based polymer isocyanate adhesives are inadequate in water-resistant adhesion, especially boiling water-resistant adhesion, although they are satisfactory in dry adhesion. Another challenge is an environment that is more severe than conventional environments, such as high temperatures or high humidity for extended periods of time.

In addition to the requirement of adhesion, an extension of stability (pot life) of the adhesive itself after an isocyanate compound is blended is desired.

<CIT> relates to a water-based polymer dispersion for isocyanate-crosslinked adhesives comprising a polymer (<NUM>) which is obtained by emulsion polymerization of a monomer composition comprising at least one monomer selected from the group consisting of an aromatic vinyl monomer and a (meth)acrylate monomer, a crosslinkable monomer, and a different monomer; and a polymer (<NUM>) which is obtained by emulsion polymerization of a monomer composition comprising at least one monomer selected from the group consisting of an aromatic vinyl monomer and a (meth)acrylate monomer, a hydroxyl group-containing vinyl monomer, an ethylenically unsaturated carboxylic acid monomer, and a different monomer, wherein the polymers (<NUM>) and (<NUM>) have a Tg difference of <NUM> to <NUM>.

<CIT> relates to a copolymer latex for aqueous polymer isocyanate-based adhesives.

It is an object of the present invention to provide a polymer latex for use in adhesive compositions, which provide long pot life after mixing with the hardener component and to provide a high wood joint strength, which is suitable for use in wood glue and in particular in D4 wood glue.

The following clauses summarize some aspects of the present invention.

According to a first aspect, the present invention relates to a polymer latex for use in an adhesive composition, obtainable by free-radical emulsion polymerization of a mixture of ethylenically unsaturated monomers comprising:.

wherein the weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) is in the range of from <NUM> to <NUM>; and wherein the polymer latex has a median particle size of at least <NUM>, wherein the median particle size is determined by dynamic light scattering according to ISO <NUM>:<NUM>.

The sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may be in the range of from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, based on the total weight of the monomers in the monomer mixture.

The mixture of ethylenically unsaturated monomers may comprise:.

The vinyl aromatic monomer (a) may be selected from styrene, alpha-methyl styrene, vinyl toluene and combinations thereof. The vinyl aromatic monomer (a) may be selected from styrene.

The mixture of ethylenically unsaturated monomers may comprise:
(b) <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of the conjugated diene monomer, based on the total weight of the monomers in the monomer mixture.

The conjugated diene monomer (b) may be selected from <NUM>,<NUM>-butadiene, isoprene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butadiene, <NUM>-chloro-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-pentadiene, <NUM>,<NUM>-hexadiene, <NUM>,<NUM>-hexadiene, <NUM>,<NUM>-octadiene, <NUM>-methyl-<NUM>,<NUM>-pentadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-pentadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-hexadiene, <NUM>,<NUM>-diethyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-diethyl-<NUM>,<NUM>-octadiene, <NUM>-butyl-<NUM>,<NUM>-octadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>-methyl-<NUM>-methylene-<NUM>,<NUM>-octadiene, <NUM>-methyl-<NUM>-methylene-<NUM>,<NUM>-octadiene, <NUM>,<NUM>,<NUM>-octatriene, <NUM>-ethyl-<NUM>,<NUM>-butadiene, <NUM>-amyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>,<NUM>,<NUM>-trimethyl-<NUM>,<NUM>,<NUM>,<NUM>-dodecatetraene, <NUM>,<NUM> -dimethyl-<NUM>-methylene-<NUM>,<NUM>,<NUM>-dodecatriene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>-phenyl-<NUM>,<NUM>-butadiene, <NUM>-methyl-<NUM>-isopropyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-cyclohexadiene, myrcene, ocimene, farnesene and combinations thereof. The conjugated diene monomer (b) may be selected from <NUM>,<NUM>-butadiene, isoprene and combinations thereof. The conjugated diene monomer (b) may be selected from <NUM>,<NUM>-butadiene.

The mixture of ethylenically unsaturated monomers may comprise:
(c) <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of the ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group, based on the total weight of the monomers in the monomer mixture.

The ethylenically unsaturated monomer having an acid functional group (c) may be selected from ethylenically unsaturated carboxylic acid monomers, ethylenically unsaturated sulfonic acid monomers, ethylenically unsaturated phosphorous-containing acid monomers. The ethylenically unsaturated monomer having an acid functional group (c) may be selected from (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, vinyl acetic acid, vinyl lactic acid, vinyl sulfonic acid, styrene sulfonic acid, <NUM>-carboxy ethyl (meth)acrylate, phenyl vinyl sulfonate, sodium <NUM>-vinyl benzenesulfonate, <NUM>-methyl-<NUM>-propene-<NUM>-sulfonic acid, <NUM>-propene-<NUM>-sulfonic acid, <NUM>-styrenesulfonic acid, <NUM>-acrylamido-<NUM>-methyl-<NUM>-propanesulfonic acid, vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allylphosphonate, allylphosphonic acid, and combinations thereof. The ethylenically unsaturated monomer having an acid functional group (c) may be selected from (meth)acrylic acid, itaconic acid, and combinations thereof.

The ethylenically unsaturated monomer having a hydroxyl functional group (c) may be selected from allyl alcohol, vinyl alcohol, N-methylol (meth)acrylamide, <NUM>-penten-<NUM>-ol, hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethylcaprolactone acrylate, and combinations thereof. The ethylenically unsaturated monomer having a hydroxyl functional group (c) may be selected from hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethylcaprolactone acrylate. The ethylenically unsaturated monomer having a hydroxyl functional group (c) may be selected from hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl methacrylate, and combinations thereof.

The ethylenically unsaturated monomer having an acid and hydroxy functional group (c) may be selected from <NUM>-allyloxy-<NUM>-hydroxy-<NUM>-propanesulfonic acid.

The weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) may be in the range of from <NUM> to <NUM>.

The polymer latex may have a median particle size of at least <NUM>, preferably of at least <NUM>.

The mixture of ethylenically unsaturated monomers may comprise <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of a chain transfer agent, wherein the weight percentage is based on the total amount of monomers in the monomer mixture.

The chain transfer agent may be selected from n-dodecyl mercaptan, carbon tetrachloride, carbon tetrabromide, bromotrichloro methane, <NUM>-methylbenzenethiol, isooctyl <NUM>-mercaptopropionate, tert-nonyl mercaptan, <NUM>,<NUM>'-thiobisbenzenethiol, tert-dodecyl mercaptan, alpha-methyl styrene dimer, thioglycolic acid, <NUM>-ethylhexyl thioglycolate, butyl <NUM>-mercaptopropionate, <NUM>,<NUM>-dimercapto-<NUM>,<NUM>-dioxa octane and combinations thereof, preferably tert-dodecyl mercaptan.

The mixture of ethylenically unsaturated monomers may further comprise (d) <NUM> to <NUM> wt. -% of an ethylenically unsaturated monomer different from (a) to (c), based on the total weight of the monomers in the monomer mixture; wherein the ethylenically unsaturated monomer different from (a) to (c) preferably is selected from.

According to a further aspect, the invention relates to a method for preparing a polymer latex, preferably as discussed above, for the use in adhesives, comprising:.

The sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may be in the range of from <NUM> to <NUM> w. -%, preferably from <NUM> to <NUM> wt. -%, based on the total weight of the monomers in the monomer mixture.

The conjugated diene monomer (b) may be selected from <NUM>,<NUM>-butadiene, isoprene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butadiene, <NUM>-chloro-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-pentadiene, <NUM>,<NUM>-hexadiene, <NUM>,<NUM>-hexadiene, <NUM>,<NUM>-octadiene, <NUM>-methyl-<NUM>,<NUM>-pentadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-pentadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-hexadiene, <NUM>,<NUM>-diethyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-diethyl-<NUM>,<NUM>-octadiene, <NUM>-butyl-<NUM>,<NUM>-octadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>-methyl-<NUM>-methylene-<NUM>,<NUM>-octadiene, <NUM>-methyl-<NUM>-methylene-<NUM>,<NUM>-octadiene, <NUM>,<NUM>,<NUM>-octatriene, <NUM>-ethyl-<NUM>,<NUM>-butadiene, <NUM>-amyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>- octatriene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>,<NUM>,<NUM>- trimethyl-<NUM>,<NUM>,<NUM>,<NUM>-dodecatetraene, <NUM>,<NUM>-dimethyl-<NUM>-methylene-<NUM>,<NUM>,<NUM>-dodecatriene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>-phenyl-<NUM>,<NUM>-butadiene, <NUM>-methyl-<NUM>-isopropyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-cyclohexadiene, myrcene, ocimene, farnesene and combinations thereof. The conjugated diene monomer (b) may be selected from <NUM>,<NUM>-butadiene, isoprene and combinations thereof. The conjugated diene monomer (b) may be selected from <NUM>,<NUM>-butadiene.

The mixture of ethylenically unsaturated monomers may comprise <NUM> to
<NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of a chain transfer agent, wherein the weight percentage is based on the total amount of monomers in the monomer mixture. The chain transfer agent may be selected from n-dodecyl mercaptan, carbon tetrachloride, carbon tetrabromide, bromotrichloro methane, <NUM>-methylbenzenethiol, isooctyl <NUM>-mercaptopropionate, tert-nonyl mercaptan, <NUM>,<NUM>'-thiobisbenzenethiol, tert-dodecyl mercaptan, alpha-methyl styrene dimer, thioglycolic acid, <NUM>-ethylhexyl thioglycolate, butyl <NUM>-mercaptopropionate, <NUM>,<NUM>-dimercapto-<NUM>,<NUM>-dioxa octane and combinations thereof, preferably tert-dodecyl mercaptan.

Another aspect of the present invention relates to use of the polymer latex as discussed above or prepared by the method as discussed above for the preparation of an aqueous adhesive composition, preferably a two-component aqueous adhesive composition.

In addition, a further aspect of the present invention relates to an aqueous adhesive composition comprising (i) the polymer latex as discussed above or prepared by the method as discussed above and (ii) a polyisocyanate compound.

The (ii) polyisocyanate compound may comprise toluene diisocyanate, hydrogenated toluene diisocyanate, methylene diphenyl diisocyanate, hydrogenated methylene diphenyl diisocyanate, triphenylmethane triisocyanate, <NUM>,<NUM>,<NUM>-benzene triisocyanate, polymethylene polyphenyl polyisocyanate, xylene diisocyanate, tetramethyl xylylene diisocyanate, <NUM>,<NUM>-hexamethylene diisocyanate, <NUM>,<NUM>,<NUM>-trimethyl hexamethylene diisocyanate, <NUM>,<NUM>,<NUM>-trimethyl hexamethylene diisocyanate, isophorone diisocyanate, and <NUM>,<NUM>'-methylene-bis(cyclohexyl isocyanate), and combinations thereof.

The aqueous adhesive composition as discussed above may further comprise polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, such as methylcellulose, ethylcellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starches, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof, preferably polyvinyl alcohol.

The aqueous adhesive composition as discussed above may be a two-component adhesive composition, wherein a first component comprises the polymer latex and optionally polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, such as methylcellulose, ethylcellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starches, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof, preferably polyvinyl alcohol; and a second component comprises the polyisocyanate compound.

The aqueous adhesive composition as discussed above may comprise from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -% of the polyisocyanate compound (ii), based on the total solids content of the aqueous adhesive composition.

The aqueous adhesive as discussed above may be in the form of a wood glue. Another aspect of the present invention relates to a method of preparing an aqueous adhesive composition comprising:
providing (i) the polymer latex as discussed above or prepared by the method as discussed above; and mixing with a (ii) polyisocyanate compound, wherein the aqueous adhesive composition preferably is a wood glue.

The present invention relates to a polymer latex for use in an adhesive composition. The polymer latex is obtainable by free-radical emulsion polymerization of a mixture of ethylenically unsaturated monomers comprising: (a) a vinyl aromatic monomer; (b) a conjugated diene monomer; and (c) an ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group. According to the present invention, the weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) is in the range of from <NUM> to <NUM>. The polymer latex of the present invention has a median particle size of at least <NUM>. The median particle size is determined by dynamic light scattering according to ISO <NUM>:<NUM>, e.g., with the dynamic light scattering instrument Mastersizer <NUM> (Malvern Panalytical (United Kingdom)). The polymer latex preferably is obtained by free-radical emulsion polymerization of a mixture of ethylenically unsaturated monomers comprising: (a) a vinyl aromatic monomer; (b) a conjugated diene monomer; and (c) an ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group.

It has surprisingly been found, that the weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) as well as the median particle size of the polymer latex of the present invention provide for improved wood joint strength as well as improved pot life.

According to the present invention, the sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may be at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, based on the total weight of the monomers in the monomer mixture. The sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may be <NUM> wt. -% or less, such as <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less, based on the total weight of the monomers in the monomer mixture. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) can be in the range of from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -%, even more preferably from <NUM> to <NUM> wt. -%, most preferably from <NUM> to <NUM> wt. -%, based on the total weight of the monomers in the monomer mixture.

The mixture of the ethylenically unsaturated monomers of the present invention may comprise (a) at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -% of the vinyl aromatic monomer, based on the total weight of the monomers in the monomer mixture. The mixture of the ethylenically unsaturated monomers of the present invention may comprise (a) <NUM> wt. -% or less, such as <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less of the vinyl aromatic monomer, based on the total weight of the monomers in the monomer mixture. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the mixture of ethylenically unsaturated monomers may comprise (a) <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, most preferably <NUM> to <NUM> wt. -% of the vinyl aromatic monomer, based on the total weight of the monomers in the monomer mixture.

According to the present invention, the vinyl aromatic monomer (a) may be selected from styrene, alpha-methyl styrene, vinyl toluene and combinations thereof. Preferably the vinyl aromatic monomer (a) may be styrene.

The mixture of the ethylenically unsaturated monomers of the present invention may comprise (b) at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -% of the conjugated diene monomer, based on the total weight of the monomers in the monomer mixture. The mixture of the ethylenically unsaturated monomers of the present invention may comprise (b) <NUM> wt. -% or less, such as <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less of the conjugated diene monomer, based on the total weight of the monomers in the monomer mixture. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the mixture of ethylenically unsaturated monomers may comprise (b) <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, even more preferably <NUM> to <NUM> wt. -%, most preferably <NUM> to <NUM> wt. -% of the conjugated diene monomer, based on the total weight of the monomers in the monomer mixture.

According to the present invention, the conjugated diene monomer (b) may be selected from <NUM>,<NUM>-butadiene, isoprene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-butadiene, <NUM>-chloro-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-pentadiene, <NUM>,<NUM>-hexadiene, <NUM>,<NUM>-hexadiene, <NUM>,<NUM>-octadiene, <NUM>-methyl-<NUM>,<NUM>-pentadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-pentadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-hexadiene, <NUM>,<NUM>-diethyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-diethyl-<NUM>,<NUM>-octadiene, <NUM>-butyl-<NUM>,<NUM>-octadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>-methyl-<NUM>-methylene-<NUM>,<NUM>-octadiene, <NUM>-methyl-<NUM>-methylene-<NUM>,<NUM>-octadiene, <NUM>,<NUM>,<NUM>-octatriene, <NUM>-ethyl-<NUM>,<NUM>-butadiene, <NUM>-amyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>- octatriene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>,<NUM>,<NUM>- trimethyl-<NUM>,<NUM>,<NUM>,<NUM>-dodecatetraene, <NUM>,<NUM>-dimethyl-<NUM>-methylene-<NUM>,<NUM>,<NUM>-dodecatriene, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>,<NUM>-octatriene, <NUM>-phenyl-<NUM>,<NUM>-butadiene, <NUM>-methyl-<NUM>-isopropyl-<NUM>,<NUM>-butadiene, <NUM>,<NUM>-cyclohexadiene, myrcene, ocimene, farnesene and combinations thereof, preferably <NUM>,<NUM>-butadiene, isoprene and combinations thereof. The conjugated diene monomer (b) may be <NUM>,<NUM>-butadiene.

The mixture of the ethylenically unsaturated monomers of the present invention may comprise (c) at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -% of the ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group, based on the total weight of the monomers in the monomer mixture. The mixture of the ethylenically unsaturated monomers of the present invention may comprise (c) <NUM> wt. -% or less, such as <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less of the ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group, based on the total weight of the monomers in the monomer mixture. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the mixture of ethylenically unsaturated monomers may comprise (c) <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, even more preferably <NUM> to <NUM> wt. -%, most preferably <NUM> to <NUM> wt. -% of the ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group, based on the total weight of the monomers in the monomer mixture.

The ethylenically unsaturated monomer having an acid functional group (c), which can be used in the present invention, may be selected from ethylenically unsaturated carboxylic acid monomers, ethylenically unsaturated sulfonic acid monomers, ethylenically unsaturated phosphorous-containing acid monomers, and combinations thereof. The ethylenically unsaturated carboxylic acid monomers suitable for use in the present invention may include monocarboxylic acid and dicarboxylic acid monomers, monoesters of dicarboxylic acid, carboxy alkyl esters of ethylenically unsaturated acids such as <NUM>-carboxy ethyl (meth)acrylate, and ethylenically unsaturated carboxylic acid derivatives such as ethylenically unsaturated dicarboxylic acid anhydrides. Carrying out the present invention, it is preferable to use ethylenically unsaturated aliphatic mono- or dicarboxylic acids or anhydrides which contain from <NUM> to <NUM> carbon atoms. Examples of monocarboxylic acid monomers include (meth)acrylic acid, crotonic acid and examples of dicarboxylic acid monomers including fumaric acid, itaconic acid, maleic acid and maleic anhydride.

Examples of ethylenically unsaturated sulfonic acid monomers include vinyl sulfonic acid, phenyl vinyl sulfonate, sodium <NUM>-vinylbenzenesulfonate, <NUM>-methyl-<NUM>-propene-<NUM>-sulfonic acid, <NUM>-propene-<NUM>-sulfonic acid, <NUM>-styrenesulfonic acid, <NUM>-allyloxy-<NUM>-hydroxy-<NUM>-propanesulfonic acid, <NUM>-acrylamido-<NUM>-methyl-<NUM>-propanesulfonic acid and the salts thereof.

Examples of ethylenically unsaturated phosphorus-containing acid monomers include vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allyl phosphonate, allyl phosphonic acid and the salts thereof.

Preferably, the ethylenically unsaturated monomer having an acid functional group (c) is selected from ethylenically unsaturated carboxylic acid monomers, ethylenically unsaturated sulfonic acid monomers, ethylenically unsaturated phosphorous-containing acid monomers, and combinations thereof, preferably from (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, vinyl acetic acid, vinyl lactic acid, vinyl sulfonic acid, styrene sulfonic acid, <NUM>-carboxy ethyl (meth)acrylate, phenyl vinyl sulfonate, sodium <NUM>-vinyl benzenesulfonate, <NUM>-methyl-<NUM>-propene-<NUM>-sulfonic acid, <NUM>-propene-<NUM>-sulfonic acid, <NUM>-styrenesulfonic acid, <NUM>-acrylamido-<NUM>-methyl-<NUM>-propanesulfonic acid, vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allylphosphonate, allylphosphonic acid, and combinations thereof. More preferably, the ethylenically unsaturated monomer having an acid functional group (c) is selected from (meth)acrylic acid, itaconic acid, and combinations thereof.

The ethylenically unsaturated monomer having a hydroxyl functional group (c), which can be used in the present invention, may be selected from allyl alcohol, vinyl alcohol, N-methylol (meth)acrylamide, <NUM>-penten-<NUM>-ol, hydroxyalkyl esters of ethylenically unsaturated acids and combinations thereof, preferably hydroxyalkyl esters of ethylenically unsaturated acids.

The hydroxyalkyl esters of ethylenically unsaturated acids may include hydroxyalkyl acrylate and methacrylate monomers which are based on ethylene oxide, propylene oxide and higher alkylene oxides or mixtures thereof. Suitable examples of hydroxyalkyl esters of ethylenically unsaturated acids may be selected from hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyethylcaprolactone acrylate, and combinations thereof.

The ethylenically unsaturated monomer having an acid and a hydroxyl functional group (c), which can be used in the present invention, may be selected from <NUM>-allyloxy-<NUM>-hydroxy-<NUM>-propane sulfonic acid.

The ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group (c), which can be used in the present invention, may be selected from (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, maleic anhydride, vinyl acetic acid, vinyl lactic acid, vinyl sulfonic acid, styrene sulfonic acid, <NUM>-carboxy ethyl (meth)acrylate, phenyl vinyl sulfonate, sodium <NUM>-vinylbenzenesulfonate, <NUM>-methyl-<NUM>-propene-<NUM>-sulfonic acid, <NUM>-propene-<NUM>-sulfonic acid, <NUM>-styrenesulfonic acid, <NUM>-acrylamido-<NUM>-methyl-<NUM>-propanesulfonic acid, vinyl phosphonic acid, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diethyl allyl phosphonate, allyl phosphonic acid, allyl alcohol, vinyl alcohol, N-methylol (meth)acrylamide, <NUM>-penten-<NUM>-ol, hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethylcaprolactone acrylate, and <NUM>-allyloxy-<NUM>-hydroxy-<NUM>-propane sulfonic acid, preferably (meth)acrylic acid, itaconic acid, hydroxyalkyl esters of ethylenically unsaturated acids, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and hydroxyethylcaprolactone acrylate, and combinations thereof, more preferably (meth)acrylic acid, itaconic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and combinations thereof.

According to the present invention, the mixture of ethylenically unsaturated monomers may comprise:.

According to the present invention, the weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) is at least <NUM>, such as at least <NUM>, or at least <NUM>, or at least <NUM>, or at least <NUM>. The weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) is no more than <NUM>, such as no more than <NUM>, or no more than <NUM>, or no more than <NUM>, or no more than <NUM>. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) may be in the range of from <NUM> to <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, most preferably <NUM> to <NUM>.

According to the present invention, the polymer latex has a median particle size of at least <NUM>, preferably at least <NUM>, more preferably of at least <NUM>. The polymer latex may have a median particle size of no more than <NUM>, such as no more than <NUM>, or no more than <NUM>. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the polymer latex may have a median particle size in a range of <NUM> to <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>. The median particle size is determined by dynamic light scattering according to ISO <NUM>:<NUM>, e.g., with the dynamic light scattering instrument Mastersizer <NUM> (Malvern Panalytical (UK)).

The mixture of ethylenically unsaturated monomers may comprise a chain transfer agent. According to the present invention, the mixture of the ethylenically unsaturated monomers may comprise at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -% of a chain transfer agent, wherein the weight percentage is based on the total amount of monomers in the monomer mixture. The mixture of the ethylenically unsaturated monomers may comprise <NUM> wt. -% or less, such as <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less of a chain transfer agent, wherein the weight percentage is based on the total amount of monomers in the monomer mixture. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the mixture of the ethylenically unsaturated monomers may comprise from <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of a chain transfer agent, wherein the weight percentage is based on the total amount of monomers in the monomer mixture.

The chain transfer agent may be selected from n-dodecyl mercaptan, carbon tetrachloride, carbon tetrabromide, bromotrichloro methane, <NUM>-methylbenzenethiol, isooctyl <NUM>-mercaptopropionate, tert-nonyl mercaptan, <NUM>,<NUM>'-thiobisbenzenethiol, tert-dodecyl mercaptan, alpha-methyl styrene dimer, thioglycolic acid, <NUM>-ethylhexyl thioglycolate, butyl <NUM>-mercaptopropionate, <NUM>,<NUM>-dimercapto-<NUM>,<NUM>-dioxa octane and combinations thereof, more preferably tert-dodecyl mercaptan.

The mixture of the ethylenically unsaturated monomers may further comprise (d) an ethylenically unsaturated monomer different from (a) to (c). According to the present invention, the mixture of ethylenically unsaturated monomers may further comprise (d) <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of an ethylenically unsaturated monomer different from (a) to (c), based on the total weight of the monomers in the monomer mixture. The ethylenically unsaturated monomer different from (a) to (c) may be selected from (d1) an ethylenically unsaturated nitrile compound, (d2) an alkyl ester of ethylenically unsaturated acid, (d3) an ethylenically unsaturated compound bearing a primary or secondary amino group, and combinations thereof.

The ethylenically unsaturated nitrile compound (d1) may be selected from (meth)acrylonitrile, alpha-cyanoethyl acrylonitrile, fumaronitrile, alpha-chloronitrile and combinations thereof.

The alkyl ester of ethylenically unsaturated acid (d2) may be selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, <NUM>-ethylhexyl (meth)acrylate, and combinations thereof, preferably methyl (meth)acrylate and combinations thereof.

The ethylenically unsaturated compound bearing a primary or secondary amino group (d3) may be selected from (meth)acrylamide, <NUM>-amino ethyl (meth)acrylate hydrochloride, <NUM>-amino ethyl (meth)acrylamide hydrochloride, N-ethyl (meth)acrylamide, N-(<NUM>-amino propyl) (meth)acrylamide hydrochloride, N-hydroxyethyl (meth)acrylamide, N-<NUM>-(dimethylamino) propyl (meth)acrylamide, [<NUM>-(methacryloylamino)propyl] trimethylammonium, N-[tris(hydroxymethyl) methyl] (meth)acrylamide, N-phenylacrylamide, alkylacrylamide, methacrylamide polyethylene glycol) amine hydrochloride, and combinations thereof.

According to the present invention, the amounts of the above-defined monomers for the preparation of polymer latex may add up to <NUM> wt. -%, based on the total amount of monomers in the monomer mixture.

The present invention relates to a method for preparing a polymer latex for the use in adhesives, which comprises polymerizing by free-radical emulsion polymerization of a mixture of ethylenically unsaturated monomers. The mixture of ethylenically unsaturated monomers comprises (a) a vinyl aromatic monomer; (b) a conjugated diene monomer; and (c) an ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group. According to the present invention, the weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) is in the range of from <NUM> to <NUM>. The polymer latex of the present invention has a median particle size of at least <NUM>. The median particle size is determined by dynamic light scattering according to ISO <NUM>:<NUM>, e.g., with the dynamic light scattering instrument Mastersizer <NUM> (Malvern Panalytical (United Kingdom)).

According to the present invention, the sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may be at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, based on the total weight of the monomers in the monomer mixture. The sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) may be <NUM> wt. -% or less, such as <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less, based on the total weight of the monomers in the monomer mixture. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the sum of the vinyl aromatic monomer (a) and the conjugated diene monomer (b) can be in the range of from <NUM> to <NUM> w. -%, preferably from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -%, even more preferably from <NUM> to <NUM> wt. -%, most preferably from <NUM> to <NUM> wt. -%, based on the total weight of the monomers in the monomer mixture.

All variations with respect to the compounds used for the preparation of the polymer latex of the present invention and their relative amounts can be as described above.

The mixture of ethylenically unsaturated monomers may comprise a chain transfer agent. According to the present invention, the mixture of ethylenically unsaturated monomers may comprise at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -% of a chain transfer agent, wherein the weight percentage is based on the total amount of monomers in the monomer mixture. The mixture of ethylenically unsaturated monomers may comprise <NUM> wt. -% or less, such as <NUM> wt. -% or less, or <NUM> wt. -% or less, or <NUM> wt. -% or less of a chain transfer agent, wherein the weight percentage is based on the total amount of monomers in the monomer mixture. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the mixture of ethylenically unsaturated monomers <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of a chain transfer agent, wherein the weight percentage is based on the total amount of monomers in the monomer mixture.

The mixture of ethylenically unsaturated monomers may further comprise (d) an ethylenically unsaturated monomer different from (a) to (c). According to the present invention, the mixture of ethylenically unsaturated monomers may further comprise (d) <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -% of an ethylenically unsaturated monomer different from (a) to (c), based on the total weight of the monomers in the monomer mixture. The ethylenically unsaturated monomer different from (a) to (c) may be selected from (d1) an ethylenically unsaturated nitrile compound, (d2) an alkyl ester of ethylenically unsaturated acid, (d3) an ethylenically unsaturated compound bearing a primary or secondary amino group, and combinations thereof.

According to the present invention, the amounts of the above-defined monomers for the preparation of the polymer latex may add up to <NUM> wt. -%, based on the total amount of monomers in the monomer mixture.

The polymer latex of to the present invention can be made by any emulsion polymerization process known to a person skilled in the art, provided that the monomer mixture as herein defined is employed.

In the emulsion polymerization for preparing the polymer latex of the present invention, a seed dispersion may be employed. Any seed particles as known to the person skilled in the art can be used.

The seed particles are preferably present in an amount of <NUM> to <NUM> parts by weight, preferably <NUM> to <NUM> parts by weight, based on <NUM> parts by weight of total ethylenically unsaturated monomers employed in the polymer. The lower limit of the amount of seed particles therefore can be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> parts by weight. The upper limit of the amount can be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> parts by weight. A person skilled in the art will understand that any range formed by any of the explicitly disclosed lower limits and upper limits is explicitly encompassed in the present specification.

The process for the preparation of the above-described polymer latex can be performed at temperatures of from <NUM> to <NUM>, preferably of from <NUM> to <NUM>, particularly preferably of from <NUM> to <NUM>, very particularly preferably of from <NUM> to <NUM>, in the presence of no or one or more emulsifiers, no or one or more protective colloids and one or more initiators. The temperature includes all values and sub-values therebetween, especially including <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>.

Initiators which can be used when carrying out the present invention may include water-soluble and/or oil-soluble initiators which are effective for the purposes of the polymerization. Representative initiators are well known in the technical area and include, for example: azo compounds (such as, for example, AIBN, AMBN and cyanovaleric acid) and inorganic peroxy compounds, such as hydrogen peroxide, sodium, potassium and ammonium peroxydisulfate, peroxycarbonates and peroxyborates, as well as organic peroxy compounds, such as alkyl hydroperoxides, dialkyl peroxides, acyl hydroperoxides, and diacyl peroxides, as well as esters, such as tert-butyl perbenzoate and combinations of inorganic and organic initiators. Suitable initiators may be selected from <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-diphenylbutane, tert-butyl hydroperoxide, tert-amyl hydroperoxide, cumyl hydroperoxide, <NUM>,<NUM>,<NUM>,<NUM>-tetramethylbutyl hydroperoxide, isopropylcumyl hydroperoxide, p-menthane hydroperoxide, <NUM>,<NUM>-di(tert-butylperoxy)-<NUM>,<NUM>-dimethyl-<NUM>-hexyne, <NUM>,<NUM>,<NUM>-triethyl-<NUM>,<NUM>,<NUM>-trimethyl-<NUM>,<NUM>,<NUM>-triperoxonane, di(tert-butyl)peroxide, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-di(tert-butylperoxy)hexane, di(tert-butylperoxyisopropyl)benzene, tert-butyl cumyl peroxide, di-(tert-amyl)-peroxide, dicumyl peroxide, butyl <NUM>,<NUM>-di(tert-butylperoxy)valerate, tert-butylperoxybenzoate, <NUM>,<NUM>-di(tert-butylperoxy)butane, tert-amyl peroxy-benzoate, tert-butylperoxy-acetate, tert-butylperoxy-(<NUM>-ethylhexyl)carbonate, tert-butylperoxy isopropyl carbonate, tert-butyl peroxy-<NUM>,<NUM>,<NUM>-trimethyl-hexanoate, <NUM>,<NUM>-di(tert-butylperoxy)cyclohexane, tert-amyl peroxyacetate, tert-amylperoxy-(<NUM>-ethylhexyl)carbonate, <NUM>,<NUM>-di(tert-butylperoxy)-<NUM>,<NUM>,<NUM>-trimethylcyclohexane, <NUM>,<NUM>-di(tert-amylperoxy)cyclohexane, tert-butyl-monoperoxy-maleate, <NUM>,<NUM>'-azodi(hexahydrobenzonitrile), tert-butyl peroxy-isobutyrate, tert-butyl peroxydiethylacetate, tert-butyl peroxy-<NUM>-ethylhexanoate, dibenzoyl peroxide, tert-amyl peroxy-<NUM>-ethylhexanoate, di(<NUM>-methylbenzoyl)peroxide, <NUM>,<NUM>,<NUM>,<NUM>-tetramethylbutyl peroxy-<NUM>-ethylhexanoate, ammonium peroxodisulfate, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-di(<NUM>-ethylhexanoylperoxy)hexane, <NUM>,<NUM>'-azodi(<NUM>-methylbutyronitrile), <NUM>,<NUM>'-azodi(isobutyronitrile), didecanoyl peroxide, potassium persulfate, dilauroyl peroxide, di(<NUM>,<NUM>,<NUM>-trimethylhexanoyl) peroxide, tert-amyl peroxypivalate, tert-butyl peroxyneoheptanoate, <NUM>,<NUM>,<NUM>,<NUM>-tetramethylbutyl peroxypivalate, tert-butyl peroxypivalate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, di(<NUM>-ethylhexyl) peroxydicarbonate, di(<NUM>-tert-butylcyclohexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, tert-butyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate, tert-amyl peroxyneodecanoate, cumyl peroxyneoheptanoate, di(<NUM>-methoxybutyl) peroxydicarbonate, <NUM>,<NUM>,<NUM>,<NUM>-tetramethylbutyl peroxyneodecanoate, cumyl peroxyneodecanoate, diisobutyryl peroxide, and mixture thereof.

The initiator may be used in a sufficient amount to initiate the polymerization reaction at a desired rate. In general, an amount of initiator of from <NUM> to <NUM> wt. -%, preferably of from <NUM> to <NUM> wt. -%, based on the total weight of monomers in the monomer mixture, is sufficient. The amount of initiator is most preferably of from <NUM> to <NUM> wt. -%, based on the total weight of monomers in the monomer mixture. The amount of initiator includes all values and sub-values therebetween, especially including <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> wt. -%, based on the total weight of monomers in the monomer mixture.

The above-mentioned inorganic and organic peroxy compounds may also be used alone or in combination with one or more suitable reducing agents, as is well known in the art. Examples of such reducing agents may include sulfur dioxide, alkali metal disulfites, alkali metal and ammonium hydrogen sulfites, thiosulfates, dithionites and formaldehyde sulfoxylates, as well as hydroxylamine hydrochloride, hydrazine sulfate, iron (II) sulfate, cuprous naphthanate, glucose, sulfonic acid compounds such as sodium methane sulfonate, amine compounds such as dimethylaniline and ascorbic acid. The quantity of the reducing agent is preferably <NUM> to <NUM> parts by weight per part by weight of the polymerization initiator.

Surfactants or emulsifiers which are suitable for stabilizing the dispersion polymer may include those conventional surface-active agents for polymerization processes. The surfactant or surfactants can be added to the aqueous phase and/or the monomer phase. An effective amount of surfactant in a seed process is the amount which was chosen for supporting the stabilization of the particle as a colloid, the minimization of contact between the particles and the prevention of coagulation. In a non-seeded process, an effective amount of surfactant is the amount which was chosen for determining the particle size.

Representative surfactants include saturated and ethylenically unsaturated sulfonic acids or salts thereof, including, for example, unsaturated hydrocarbonsulfonic acid, such as vinylsulfonic acid, allylsulfonic acid and methallylsulfonic acid, and salts thereof; aromatic hydrocarbon acids, such as, for example, p-styrenesulfonic acid, isopropenylbenzenesulfonic acid and vinyloxybenzenesulfonic acid and salts thereof; sulfoalkyl esters of acrylic acid and methacrylic acid, such as, for example, sulfoethyl methacrylate and sulfopropyl methacrylate and salts thereof, and <NUM>-acrylamido-<NUM>-methylpropanesulfonic acid and salts thereof; alkylated diphenyl oxide disulfonates, sodium dodecylbenzenesulfonates and dihexyl or dioctyl esters of sodium sulfosuccinate, sodium alkyl esters of sulfonic acid, ethoxylated alkylphenols and ethoxylated alcohols; fatty alcohol sulfates and fatty alcohol (poly)ether sulfates.

The type and the amount of the surfactant is governed typically by the number of particles, their size and their composition. Typically, the surfactant is used in amounts of from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -%, based on the total weight of the monomers in the monomer mixture. The amount of surfactant includes all values and sub-values therebetween, especially including <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> wt. -%, based on the total weight of the monomer in the monomer composition. The polymerization may be conducted without using surfactants.

The polymer latex of the present invention may further comprise protective colloids. The protective colloids may comprise polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, such as methylcellulose, ethylcellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starches, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof. The protective colloids may stabilize the polymer latex in addition or instead of the surfactants as described above. The protective colloids may be present during the polymerization or post-added. Typical quantities are <NUM> to <NUM> parts by weight, based on <NUM> parts by weight of the polymer latex.

The present invention relates to the use of the polymer latex of the present invention as described above or prepared by the method of the present invention as described above for the preparation of an aqueous adhesive composition.

Preferably, the aqueous adhesive composition of the present invention is a two-component composition.

As used herein, a "two-component" or "<NUM>" composition is a composition in which at least a portion of the reactive components readily react and at least partially cure without activation from an external energy source, such as at ambient temperatures, e.g., temperatures in the range of from <NUM> to <NUM>, or slightly elevated temperatures, e.g., temperatures in the range of <NUM> ° to <NUM>, when mixed. One of skill in the art understands that the two components of the composition are stored separately from each other and mixed just prior to application of the composition.

As used herein, the term "aqueous" refers to a medium that either consists exclusively of water or comprises predominantly water (e.g., at least <NUM> wt. -% water) in combination with a non-aqueous solvent. Non-aqueous solvents may be employed in the aqueous adhesive composition of the invention in small amount if desired. The amount of non-aqueous solvents may be <NUM> wt. -% or less, preferably <NUM> wt. -% or less, more preferably <NUM> wt. -% or less, most preferably <NUM> wt. -% or less, and in particular <NUM> wt. or less based on the solids content of the aqueous adhesive composition. Examples of suitable non-aqueous solvents include, but are not limited to, toluene, acetone, methylethylketone, cyclohexane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ether, dimethylformamide, dimethyl sulfoxide, monohydric alcohols such as methanol and ethanol, and polyhydric alcohols. The aqueous adhesive composition is preferably free of non-aqueous solvents.

Furthermore, the present invention relates to an aqueous adhesive composition comprising (i) the polymer latex of the present invention as described above or prepared by the method of the present invention as described above and (ii) a polyisocyanate compound.

All variations with respect to the polymer latex and to the compounds used for the preparation of the polymer latex of the present invention and their relative amounts can be as described above.

According to the present invention, the aqueous adhesive composition may comprise at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -% of the polymer latex (i), based on the total solids content of the aqueous adhesive composition. The aqueous adhesive composition may comprise up to <NUM> wt. -%, such as up to <NUM> wt. -%, or up to <NUM> wt. -%, or up to <NUM> wt. -%, or up to <NUM> wt. -% of the polymer latex (i), based on the total solids content of the aqueous adhesive composition. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the aqueous adhesive composition may comprise from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -% of the polymer latex (i), based on the total solids content of the aqueous adhesive composition.

As used herein, the term "polyisocyanate" refers to a compound having more than one isocyanate group per molecule, e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more isocyanate groups per molecule. Suitable polyisocyanates can be aliphatic, aromatic, or a mixture thereof. The polyisocyanate may comprise toluene diisocyanate, hydrogenated toluene diisocyanate, methylene diphenyl diisocyanate, hydrogenated methylene diphenyl diisocyanate, triphenylmethane triisocyanate, <NUM>,<NUM>,<NUM>-benzene triisocyanate, polymethylene polyphenyl polyisocyanate, xylene diisocyanate, tetramethyl xylylene diisocyanate, <NUM>,<NUM>-hexamethylene diisocyanate, <NUM>,<NUM>,<NUM>-trimethyl hexamethylene diisocyanate, <NUM>,<NUM>,<NUM>-trimethyl hexamethylene diisocyanate, isophorone diisocyanate, and <NUM>,<NUM>'-methylene-bis(cyclohexyl isocyanate). Suitable polyisocyanates that can be used according to the present invention can be exemplified by Bayhydur and Desmodur grade polyisocyanates commercially available from Covestro (Germany), and by Suprasec grade polyisocyanates commercially available from Huntsman Corporation (USA).

The aqueous adhesive composition may comprise at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. -% of the polyisocyanate compound (ii), based on the total solids content of the aqueous adhesive composition. The aqueous adhesive composition may comprise up to <NUM> wt. -%, such as up to <NUM> wt. -%, or up to <NUM> wt. -%, or up to <NUM> wt. -%, or up to <NUM> wt. -% of the polyisocyanate compound (ii), based on the total solids content of the aqueous adhesive composition. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, aqueous adhesive composition may comprise from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -% of the polyisocyanate compound (ii), based on the total solids content of the aqueous adhesive composition.

The aqueous adhesive composition of the present invention may further comprise polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, such as methylcellulose, ethylcellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starches, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof. Preferably, the aqueous adhesive composition of the present invention further comprises polyvinyl alcohol. As used herein, the term "polyvinyl alcohol" is generally acknowledged in the art as a completely or partially hydrolyzed polyvinyl acetate. The polyvinyl alcohol may have a saponification degree of up to <NUM> %. As used herein, the term "saponification degree" refers to the ratio of a hydroxyl group with respect to the total number of the hydroxyl group and a carbonyloxy group such as an acetyloxy group in the polyvinyl alcohol. The saponification degree has to be understood as an average value meaning that mixtures of less hydrolyzed and more hydrolyzed polyvinyl alcohols can be used. Preferably, a saponification degree in the range of from <NUM> to <NUM> %, more preferably from <NUM> to <NUM> % is used. Suitable examples of polyvinyl alcohols include, but are not limited to, Poval grade polyvinyl alcohols commercially available from Kuraray (Japan).

According to the present invention, the polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, such as methylcellulose, ethylcellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starches, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof may be used in an amount of at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -%, or at least <NUM> wt. - %, based on the total solids content of the aqueous adhesive composition. The polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, such as methylcellulose, ethylcellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starches, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof may be used in an amount of up to <NUM> wt. -%, such as up to <NUM> wt. -%, or up to <NUM> wt. -%, or up to <NUM> wt. -%, based on the total solids content of the aqueous adhesive composition. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, such as methylcellulose, ethylcellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starches, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof may be used in an amount of from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, based on the total solids content of the aqueous adhesive composition.

The aqueous adhesive composition may comprise at least <NUM> wt. -%, such as at least <NUM> wt. -%, or at least <NUM> wt. -% of polyvinyl alcohol, based on the total solids content of the aqueous adhesive composition. The aqueous adhesive composition may comprise up to <NUM> wt. -%, such as up to <NUM> wt. -%, or up to <NUM> wt. -%, or up to <NUM> wt. -% of polyvinyl alcohol, based on the total solids content of the aqueous adhesive composition. A person skilled in the art will appreciate that any range between any of the explicitly disclosed lower and upper limit is herein disclosed. Accordingly, the aqueous adhesive composition may comprise from <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, of polyvinyl alcohol, based on the total solids content of the aqueous adhesive composition.

Optionally, the aqueous adhesive composition may further comprise a polymer latex different to those of the present invention, such as polyvinyl acetate, vinyl acetate-ethylene copolymer, polyurethane, acrylonitrile-butadiene copolymer, and combinations thereof, preferably polyvinyl acetate, vinyl acetate-ethylene copolymer, and combinations thereof. The aqueous adhesive composition may comprise up to <NUM> wt. -%, such as up to <NUM> wt. -%, or up to <NUM> wt. -%, or up to <NUM> wt. -%, or up to <NUM> wt. -% of the polymer latex different to those of the present invention, preferably polyvinyl acetate, vinyl acetate-ethylene copolymer, the weight percentages being based on the total solids content of the aqueous adhesive composition.

The aqueous adhesive composition may further comprise additives, such as plasticizers, antifoaming agents, thickeners, leveling agents, dispersants, colorants, water resistant additives, lubricants, pH adjusters, biocides, antioxidants, inorganic pigments, surfactants, and combinations thereof. These additives may be used in amounts in a range of from <NUM> to <NUM> wt. -%, based on the total solids content of the aqueous adhesive composition.

The aqueous adhesive composition may comprise fillers or extenders, inorganic pigments, and combinations thereof. Suitable examples of inorganic pigments, fillers or extenders include metal oxides, hydroxides, sulfides, carbonates, sulfates, or silicate compounds of magnesium, calcium, zinc, barium, titanium, aluminum, antimony, and lead, preferably calcium carbonate, kaolin, talc, titanium dioxide, aluminum hydroxide, silica, gypsum, baryta powder, alumina white, and satin white. The fillers or extenders, inorganic pigments, and combinations thereof may be used in amounts in a range of from <NUM> to <NUM> wt. -%, based on the total solids content of the aqueous adhesive composition.

According to the present invention, the aqueous adhesive composition may be a two-component adhesive composition. Typically, the first component comprises the polymer latex of the present invention and the second component comprises the polyisocyanate compound. The first component may further comprise polyvinyl alcohol, vinyl alcohol-ethylene copolymer, silanol-modified polyvinyl alcohol, cellulose derivative, such as methylcellulose, ethylcellulose, hydroxycellulose and carboxycellulose, chitin, chitosan, starches, polyethylene glycol, polypropylene glycol, polyvinyl ether, gelatin, casein, cyclodextrin, and combinations thereof. Preferably, the first component further comprises polyvinyl alcohol. The first component may further comprise additives, fillers or extenders, inorganic pigments, and combinations thereof.

The aqueous adhesive of the present invention may be in the form of a wood glue. As used herein, the term "wood glue" refers to an adhesive to tightly bond pieces of wood together. In particular, the aqueous adhesive is in the form of a D4 wood glue. As used herein, the term "D4 wood glue" refers to wood glues, which are suitable to use for interior with frequent long-term exposure to running or condensed water and/or exterior exposed to weather. According to the European Standard EN <NUM>:<NUM>, a D4 wood glue has an adhesive strength of more than <NUM> N/mm<NUM>.

The present invention further relates to a method of preparing an aqueous adhesive composition comprising: providing (i) the polymer latex of the present invention or prepared by the method of the present invention for preparing a polymer latex, and mixing with a (ii) polyisocyanate compound.

All variations with respect to the compounds used for the preparation of the aqueous adhesive composition of the present invention and their relative amounts can be as described above.

The aqueous adhesive of the present invention may be in the form of a wood glue. Preferably, the aqueous adhesive is in the form of a D4 wood glue.

The present invention will be further illustrated with reference to the following examples.

In the following all parts and percentages are based on weight unless otherwise specified.

The polymer latex compositions used in the examples and comparative examples were produced by a free radical emulsion polymerization carried out in a pressure resistant stainless-steel reactor connected to a cryostat enabling temperature control of the reactor jacket.

The initial charge in the reactor was composed of <NUM> pphm (parts by weight based on <NUM> parts of total monomer weight) deionized water and polystyrene seed with an average particle size of <NUM> (seed quantities for each example listed in Table <NUM> and Table <NUM>). After heating the initial charge to <NUM> under continuous agitation using a three-layered cross beam stirrer, the polymerization reaction was initiated by starting a feed of a <NUM> %(w/w) sodium persulfate solution (<NUM> pphm). The temperature was maintained constant at <NUM>. <NUM> minutes after starting the persulfate feed the monomers (quantities for each example listed in Table <NUM> and Table <NUM>), the chain transfer agent tert-dodecyl mercaptan and an aqueous solution of an anionic surfactant (<NUM> pphm of C<NUM>-C<NUM> alkyl aryl sulfonate) were added to the reactor at a constant feed rate over a period of five hours. Thereafter, a post activation feed with <NUM> pphm sodium persulfate to reduce the residual monomers was started and continued for one hour at a batch temperature of <NUM>. After complete sodium persulfate addition, the batch was kept at <NUM> for further <NUM> and agitated continuously. The product was then let cool down to ambient temperature, the pH was adjusted to <NUM> using a <NUM> wt. % aqueous sodium hydroxide solution and the total solids content of the final latex was adjusted to <NUM> wt. Finally, the latex was sieved over a filter cloth with <NUM> mesh width.

The particle sizes of the latexes were determined by dynamic light scattering according to ISO <NUM>:<NUM> with the dynamic light scattering instrument Mastersizer <NUM> (Malvern Panalytical (UK)).

A wood glue containing the polymer latex as obtained above was prepared. The wood glue consists of a component (i) (the wood glue compound) and a hardener component (ii).

A glass beaker was placed on a magnetic stirrer and <NUM> of cold deionized water was added to the beaker. <NUM> of polyvinyl alcohol (PVA) powder (Poval PVA-CST, commercially available from Kuraray) was slowly added to the gently agitated water and allowed to swell for <NUM> minutes. When heating up to <NUM>, the PVA dissolved. After holding the temperature for further <NUM> minutes, the solution was cooled down to <NUM>, <NUM> of sodium metabisulfite was added and dissolved. The solution was filtered. The <NUM> wt. -% PVA solution was allowed to cool down to room temperature and kept overnight.

For obtaining the component A, <NUM> of the XSBR latex, <NUM> of the dispersing agent Dispex AA <NUM> (commercially available from BASF SE (Germany)), <NUM> of the wetting agent Lumiten I-SC (commercially available from BASF SE (Germany)), <NUM>,<NUM> of the defoamer Foamaster <NUM> (commercially available from BASF SE (Germany)), <NUM> of the PVA solution from step <NUM> and <NUM> of <NUM> mesh calcium carbonate powder (ExCal <NUM>, commercially available from R. Carroll, Inc. (USA)) were mixed and adjusted to <NUM> wt. -% solid content with <NUM> of water. The pH was around <NUM> to <NUM> and the Brookfield viscosity RVT <NUM> rpm, spindle <NUM> was in a range between <NUM>,<NUM> and <NUM>,<NUM> cPoise.

The final wood glue formulation was obtained by a homogenizing <NUM> wt. -% of component (i) with <NUM> wt. -% of a polymeric diphenyl methane diisocyanate (Desmodur 44V20L, commercially available from Covestro (Germany)).

As explained above, the inventive wood glue is a <NUM> system and undergoes curing starting from the moment of mixing the two wood glue components (i) and (ii). The progressing curing causes a steady increase of the wood glue viscosity with the time. Above a certain limit the viscosity does not allow proper wood glue application anymore. The critical viscosity threshold is defined with a value of <NUM>,<NUM> cPoise. For practical reasons (e.g. unintended line stop), a pot life of <NUM> minutes is the minimum requirement from the view of laminated wood manufacturing, particularly the automated processing using robotic dispensers. Any value above <NUM> minutes is beneficial.

One minute after component (i) and (ii) have been mixed, Brookfield viscosity RVT <NUM> rpm, spindle <NUM> of the wood glue was determined. The viscosity steadily increased with time. The viscosity increase was monitored in <NUM> intervals, until the threshold value of <NUM>,<NUM> cPoise was reached. The result was the period from the first measurement one minute after mixing until the first result above <NUM>,<NUM> cPoise was reached.

This test was carried out according to the European Standard EN <NUM>:<NUM>. This European Standard describes tests for adhesives for the assessment of their resistance to hot and cold water. Here bonds with a thin bond-line were assessed. Panels of beech wood of the dimensions according to EN <NUM>:<NUM> were glued together with the aid of the wood glues, firmly pressed, conditioned in a standard atmosphere (<NUM> ± <NUM> and <NUM> ±<NUM> % relative humidity) for <NUM> days and finally cut to obtain test pieces suitable for tensile shear testing. <NUM> test pieces with each glue were prepared and the mean value of the valid results calculated. Before determining the bond strengths with a tensile shear tester, the wood test pieces were subjected to conditions of the resistance class D4 in accordance with the European Standard EN <NUM>:<NUM>. The wood test pieces were subjected <NUM> days in standard atmosphere (<NUM> ± <NUM> and <NUM> ±<NUM> % relative humidity) followed by <NUM> hours in boiling water and subsequently <NUM> hours in water at <NUM> ± <NUM>.

The test pieces were tested in a tensile test machine (zwickiLine Z5. <NUM> TS, commercially available from Zwick Roell (Germany)), capable of reaching a constant rate of traverse with a rate of <NUM>/min.

According to the European Standard EN <NUM>:<NUM>, the minimum adhesive strength for a D4 durability class is more than <NUM> N/mm<NUM>.

The results of pot life and wood joint strength of wood glues comprising the XSBR latexes of Examples <NUM> to <NUM> are shown in Table <NUM> and Table <NUM>.

Claim 1:
A polymer latex for use in an adhesive composition, obtainable by free-radical emulsion polymerization of a mixture of ethylenically unsaturated monomers comprising:
(a) a vinyl aromatic monomer;
(b) a conjugated diene monomer; and
(c) an ethylenically unsaturated monomer having an acid and/or a hydroxyl functional group;
wherein the weight ratio of the vinyl aromatic monomer (a) to the conjugated diene monomer (b) is in the range of from <NUM> to <NUM>; and
wherein the polymer latex has a median particle size of at least <NUM>,
wherein the median particle size is determined by dynamic light scattering according to ISO <NUM>:<NUM>.