NOVEL DISPERSIBLE ACTIVE SIZING COMPOSITIONS

Abstract: A water dispersible active sizing composition comprises an active size such as alkyl succinic acid and an effective proportion (e.g. 10-30% by weight) of a dispersant therefor, said dispersant comprising a polyalkoxylate of a rosin or forti­ fied rosin, and/or a water dispersible organic derivative thereof such as a maleinate or succinate half ester.

Description: The present invention relates to active sizes containing a reactive sizing agent and a dispersant. Traditionally, paper has been sized with rosin in conjunction with alum, which acts as a precipitant. More recently, reactive sizes have been introduced, in which the rosin has been at least partially replaced by a sizing agent which reacts directly with cellulose. The two principal reactive sizes in common use are ketene dimer and alkenyl succinic anhydrides. Typically, the latter are adducts of maleic anhydride and an olefin having from 10 to 22 carbon atoms. Reactive sizes are typically used as emulsions in water in conjunction with dispersants, which serve to stabilise the emulsion, and retention agents, which promote retention of the size on the paper. In practice, the only dispersant commonly used, at least with alkenyl succinic anhydrides, has been cationic starch. This has necessitated preparation of the emulsion on site, i.e. at the paper mill, using special plant to heat the starch/water mixture involved. It has been suggested that certain nonionic surfactants, including alcohol ethoxylates, could be used as dispersants for reactive sizes, but most known surfactant-containing reactive sizes give poor sizing performance and/or rapid sedimentation. We have now discovered a method for dispersing reactive sizing agents using rosin-based dispersants, which yields water-dispersible compositions having a reduced tendency to sedimentation and providing particularly effective sizing, the dispersant actually tending to enhance the sizing efficiency synergistically. GB-A-2140049 describes the preparation of polyethylene glycol di-esters derived from a polyethylene glycol and a monocarboxylic acid which can be abietic acid. According to this invention, a method is provided for the manufacture of a dispersant for use, in conjunction with a reactive sizing agent, in the preparation of a water-dispersible active size composition which comprises the reactive sizing agent, the dispersant and, optionally, a retention agent, characterised in that the dispersant comprises a polyalkyoxylate of a fortified rosin and is made by reacting a fortified rosin with a polyalkylene glycol in a proportion up to the stoichiometric amount, per mole of fortified rosin acid, such that the resultant product is essentially free from terminal alcoholic hydroxyl groups and contains at least one compound having the formula H₃-n R (X m-1 (CH₂) p R¹) n wherein R is a fortified levopimarate group, each X is an ethyleneoxy or propyleneoxy group, R¹ represents _OR² (in which R² is a C₁ to C₂₀ saturated or unsatured hydrocarbon group) or a carboxylate group having from 1 to 20 carbon atoms, R¹ and R² being optionally substituted by one or more carboxyl, carboxylic anhydride or hydroxyl groups, n is 1, 2 or 3, m is from 4 to 30 and p is 2 or 3. Rosin comprises levopimaric acid, which is a tricyclic monocarboxylic acid having two conjugated double bonds. Levopimaric acid reacts with maleic acid or fumaric acid or their derivatives to form a tetracyclic Diels-Alder adduct with three carboxy groups. The maleinised or fumarised rosin is called fortified rosin. In carrying out the invention, the fortified rosin preferably is an at least 6% maleic or fumaric acid fortified gum or tall rosin. Typically R¹ is a dicarboxylic acid half ester group, such as a maleinate, succinate, itaconate or phthalate, or a carboxylic acid group, such as formate, acetate, propionate, hexanoate, benzoate, stearate, palmitate, acrylate, oleate or linoleate. When R¹ represents _OR², R² is typically a methyl, ethyl, propyl, butyl, lauryl, cetyl, stearyl, phenyl, nonylphenyl or benzyl group. Especially preferred are maleinate and succinate half esters formed by reacting an alcohol of the formula H 3-n R(X m-1 (CH₂) p OH) n with maleic or succinic anhydride. The applicant believes that the invention would also be operable with dispersants in which R¹ is a fumarate, malonate, adipate, pimelate, suberate, sebacate, citrate, lactate or tartrate group, but these are not preferred because they are difficult to prepare, due to non-availability of the corresponding anhydrides. Wholly or partially fortified rosin may be reacted with polyalkylene glycols to form mono-, di-, or tri- esters, which may in turn, be reacted with maleic anhydride to form the corresponding maleinate half esters. The preparation of fortified rosin and of the aforesaid esters and half esters is described in our GB-A-2155942. The dispersants which are preferred and are of particular use according to our invention are those compounds which contain from 9 to 90, more preferably 18 to 60, alkyleneoxy groups per molecule of the above formula, the molecule preferably containing two polyoxyalkylene chains, together with the corresponding maleic or succinic acid half esters. Preferably, each polyoxyalkylene chain contains an average of from 4.5 to 30 and, more preferably, 6 to 20 alkylene oxide moieties, the upper part of the above range being preferred for the mono esters and the lower part for the tris esters. Preferably, each polyalkyleneoxy chain has a molecular weight of less than 2000 and, more preferably, less than 1000. The alkylene oxide moieties are preferably derived from ethylene oxide, but those derived from propylene oxide or from mixed ethylene oxide/propylene oxide may also be used. Typically, the fortified rosin is reacted with a polyethylene glycol having a molecular weight in the range from 200 to 1,000 in proportions up to the stoichiometric amount, e.g. a proportion of 1 to 3 moles per mole of fortified rosin acid. If the molar proportion of polyethylene glycol per mole of fortified rosin acid is substantially less than 2: 1, we prefer a polyethylene glycol having a molecular weight of 400 to 1,000, most preferably 800. If the molar proportion of the glycol is substantially more than 2: 1, then a molecular weight in the range of 200 to 600, e.g. 400, is preferred. Where the molar proportion of glycol is substantially 2: 1 (e.g. it is in the range from 1.7: 1 to 2.3: 1), the molecular -weight is preferably in the range from 400 to 800, e.g. 600. Carboxylic acid anhydrides other than maleic and succinic may be used in the preparation of the half esters mentioned above, e.g. succinic, itaconic or phthalic anhydride; however, maleic anhydride is preferred. Alternatively, but less preferably, fortified rosin may be esterified with a polyethoxylated nonionic surfactant. The latter may be a polyethoxylated alcohol, such as poly-(e.g. 4 to 15 mole)-ethoxylated ceto-stearyl alcohol, polyethoxylated nonylphenol or polyethoxylated sorbitan or glyceryl esters, or a polyethoxylated fatty acid, such as palmitic, stearic, oleic or linoleic acid. The rosin may be gum or tall rosin and may be fortified with maleic or fumaric acids or with any ester-forming dienophilic derivative thereof, such as maleic anhydride, or an acid chloride or transesterifiable ester. The degree of fortification may be from 0% to 100% molar, typically from 40% to 100% molar, based on the fortifiable acid content of the rosin. The latter range corresponds to 20% to 50% molar based on the total rosin, preferably at least 30%. Typically, the rosin is reacted with from 6% to 18% by weight, preferably 10% to 16%, of maleic anhydride or fumaric acid. The reactive size may be any sizing agent which is capable of reacting directly with cellulose to give effective sizing in the absence of precipitants such as alum. The preferred reactive sizing agents are alkyl or alkenyl succinic anhydrides prepared by reacting olefins having from 6 to 22 carbon atoms, preferably 10 to 20, e.g. 12 to 18, with maleic anhydride. Other reactive sizing agents which may be used according to our invention include ketene dimer. Mixtures of reactive sizes may be used. Suitable reactive sizing products are described in, for instance, GB-A-2126260, GB-A-0141641 and GB-A-1492104. The proportion of dispersant present in the composition of our invention preferably is from 1% to 70% based on the total weight of reactive size and dispersant, more preferably 3% to 50% and most preferably 6% to 40%, e.g. 10% to 30%. The optimum amount depends upon the particular dispersant selected. Generally it is not possible to obtain adequate dispersion, or effective sizing, with less than about 1% by weight of dispersant, based on the total weight of the mixture of reactive sizing ingredient and dispersant, and the majority of such compositions require more than about 5%. Some of our dispersants are only fully effective above 10% by weight of the mixture. Most give an optimum sizing performance in concentrations between 10% and 20% by weight. Some, however, perform particularly well in concentrations up to 30% and our preferred dispersants have given highly effective sizing at dispersant concentrations greater than 40% of the weight of size and dispersant. Even relatively modest sizing performance with mixtures of size and dispersant containing, e.g. 50% or more of the dispersant is significant, since the dispersant is substantially cheaper than the reactive size, but does not itself usually exhibit sizing properties. Thus any improved sizing effect obtained with mixtures of dispersants and reactive size according to our invention is a major commercial benefit and evidence of a marked synergism. Even equivalent or only slightly poorer performance may represent a cost-effectiveness gain and indicates some synergism. In general therefore, we prefer to use the highest proportions of dispersant consistent with effective sizing. Best results have been obtained with dispersants having an average chain length greater than six ethylene oxide moieties per chain, e.g. greater than 9 ethylene oxide moieties per chain, and less than 20 ethylene oxide moieties, e.g. less than 16 per chain. Particularly preferred are the diester having an average of from 10 to 15 ethylene oxide moieties per chain, e.g. 12.5 and the monoester having an average of from 6 to 10, e.g. 8 ethylene oxide moieties per chain. Maleinate half esters generally give superior sizing action to the corresponding unmaleinated esters. The sizes of our invention are normally applied in conjunction with retention agents. These may be either anionic or typically cationic retention agents, which may optionally be present as additional components of the mixtures of our invention. Suitable materials include polyamides, polyimides, polyacrylamides and cationic starch, as well as cationic surfactants such as fatty alkyl quaternary ammonium salts. The composition of our invention may also include other additive for example antifoams, or other auxiliary chemicals. Our compositions are dispersed or emulsified prior to use by stirring with water, typically in concentrations of 0.2 to 20%, preferably 0.2 to 15%, especially 0.5 to 5 e.g. 1% by weight of organic phase based on the total weight of the emulsion. The size emulsion is then applied to paper in the conventional manner, e.g. at a concentration of from 0.1 to 1%, e.g. 0.3% on fibre, and the paper is drained by application of a draining agent. The invention is illustrated by the following examples: Examples 1 to 8 A. In each of these Examples, 100 gms of maleinated Chinese gum rosin was heated with various proportions of polyethylene glycol in the presence of 0.1 gm zinc oxide. The rosin was 16% fortified except for Example 8 which was 10% fortified. B. 100 gms of the ester product of A was in each case reacted with a substantially stoichiometric amount of maleic anhydride at 90-100°C for 1 hour to form the maleinate half ester. The details are set out in Table 1. The glycol esters of A and the maleinated half esters of B were each mixed with an alkyl succinate anhydride sizing agent at 15% concentration. All gave a clear, light brown liquid which, on stirring with water, formed stable aqueous emulsions showing little or no sedimentation during normal mill retention periods. Example 9 Mixtures of alkyl succinic anhydride size containing varying proportions of esters prepared by the general method A above or of maleinates prepared by the general method B, were each emulsitfed in water and applied to paper, at a loading of 0.25% organics based on the weight of fibre, and in conjunction with a proprietory cationic retention agent. The cobb values of the paper were measured and are shown in Table 2. The Table shows the marked synergism between the dispersant and the size. In the left hand column the prefixes refer to the number of moles of polyethylene glycol reacted with each mole of fortified rosin and the numbers refer to the molecular weight of the polyethylene glycol. Substantially similar results are obtained when the examples are repeated using fumarated gum rosin, or with maleinated or fumarated tall oil rosin. Example 10 100 gms of 16% maleinated gum rosin was heated at 260-270°C for 4-5 hours with two molar proportions of ceto stearyl alcohol ethoxylate/propoxylate. The product forms a stable emulsion with alkyl succinic anhydride sizing agent and with ketene dimer, which emulsions give effective sizing. Examples 11 to 13 Example 10 was repeated using a C₁₂₋₁₅ synthetic alcohol five mole ethoxylate (Example 11) and two polyethylene glycol alkyls (Example 12 and 13). All formed stable emulsion with active size, which gave good sizing, especially Example 11. Examples 14 to 16 In these examples 6% maleinised tall rosin was used as the feedstock. I. In each case 100 gms of fortified tall oil rosin was heated with various proportions of polyethylene glycol in the presence of 0.1 gm. zinc oxide. II. 100 gms of the ester product of I was in each case reacted with a substantially stoichiometric amounts of maleic anhydride at 90-100% for 1 hour to form the maleinate half ester. Blends were then made up of the above compounds with A.S.A. at 10% and 20% dispersant levels, and tested for water dispersibility. In each case the product gave satisfactory dispersion of A.S.A. at both 10% and 20% based on the total mixture.

Claims: 1. A method of manufacture of a dispersant for use, in conjunction with a reactive sizing agent, in the preparation of a composition which comprises the reactive sizing agent, the dispersant and, optionally, a retention agent, characterised in that the dispersant comprises a polyalkoxylate of a fortified rosin and is made by reacting a fortified rosin with a polyalkylene glycol in a proportion up to the stoichiometric amount, per mole of fortified rosin acid, such that the resultant product is essentially free from terminal alcoholic hydroxyl groups and contains at least one compound having the formula wherein R is a fortified levopimarate group, each X is an ethyleneoxy or propyleneoxy group, R¹ represents _OR² (in which R² is a C₁ to C 2O saturated or unsaturated hydrocarbon group) or a carboxylate group having from 1 to 20 carbon atoms, R¹ and R² being optionally substituted by one or more carboxyl, carboxylic anhydride or hydroxyl groups, n is 1, 2 or 3, m is from 4 to 30 and p is 2 or 3. 2. A method according to claim 1, wherein the fortified rosin is maleinised or fumarised gum or tall rosin. 3. A method according to claim 1 or 2, wherein the said formula contains from 9 to 90 alkyleneoxy groups. 4. A method according to any preceding claim, wherein each polyoxyalkylene chain of the said formula contains an average of 4.5 to 30 alkylene oxide moieties. 5. A method according to claim 4, wherein each polyoxyalkylene chain contains from 6 to 20 alkylene oxide moieties. 6. A method according to claim 3, 4 or 5, wherein each polyoxyalkylene chain has a molecular weight of less than 2000. 7. A method according to any preceding claim, wherein 1 to 3 moles of polyethylene glycol are reacted per mole of fortified rosin. 8. A method according to claim 7, wherein the molar proportion of polyethylene glycol per mole of fortified rosin is less than 2: 1 and the polyethylene glycol has a molecular weight in the range from 400 to 1000, 9. A method according to claim 7, wherein the molar proportion of polyethylene glycol per mole of fortified rosin is more than 2: 1 and the polyethylene glycol has a molecular weight in the range from 200 to 600. 10. A method according to claim 7, wherein the molar proportion of polyethylene glyocol per mole of fortified rosin is in the range from 1.7: 1 to 2.3: 1 and the polyethylene glycol has a molecular weight in the range from 400 to 800. 11. A method according to any preceding claim, wherein R¹ in the formula is a maleinate or succinate half ester group. 12. A water-dispersible active size composition comprising a reactive sizing agent, a dispersant therefor and, optionally, a cationic agent, characterised in that the dispersant is made by a method according to any preceding claim and in that the proportion by weight of the dispersant in the composition, based on the total weight of reactive sizing agent and dispersant, is in the range from 1% to 70%. 13. A composition according to claim 12, wherein the proportion by weight of the dispersant is in the range from 3% to 50%. 14. A composition according to claim 13, wherein the proportion of dispersant is in the range from 10% to 30%. 15. A composition according to any of claims 12 to 14, wherein the active sizing agent comprises an alkyl or alkenyl succinic anhydride prepared by reacting an olefin having from 6 to 22 carbon atoms per molecule with maleic anhydride. 16. An aqueous emulsion containing from 0.2% to 15% by weight of a composition according to any of claims 12 to 15. 17. A method of sizing paper, which comprises applying thereto an emulsion according to claim 16.

Inventors: JONES, MERVYN FRANCIS
Applicants: ALBRIGHT & WILSON LIMITED
Application year: 1986
Main classification: D21H17
IPC codes: D21H21, D21H17