THERMOPLASTIC ELASTOMER COMPOSITIONS HAVING BIORENEWABLE CONTENT

Thermoplastic elastomer compositions, in particular derived from one or more styrenic block copolymers wherein at least one styrenic block copolymer comprises a controlled distribution copolymer block including a conjugated diene and a mono alkenyl arene, a plurality of biorenewable materials, preferably a softener and one or more synergistic additives such as a polar polymer; a synergistic block copolymer such as a relatively high molecular weight styrenic block copolymer; and/or filler. Numerous desirable articles can be formed from the compositions. Processes for preparing the compositions and articles are disclosed.

DETAILED DESCRIPTION OF THE INVENTION

The thermoplastic elastomer compositions of the present invention include a styrenic block copolymer having a controlled distribution copolymer block having a conjugated diene and a mono alkenyl arena, wherein said block comprises terminal regions adjacent relatively harder blocks, with the controlled distribution block being rich in conjugated dienes adjacent to the relatively hard blocks and one or more regions not adjacent to the relatively hard blocks that are rich in mono alkenyl arena units, and biorenewable components comprising a softener and an additive. Surprisingly, the inventive compositions exhibit lower hardness without sacrificing much tensile strength when compared to combining the styrenic block copolymer having the controlled distribution copolymer block with a mineral oil. Polar components such as starch, PLAs, etc. have also found to help better retain the softener in various formulations. The compositions of the present invention can also include other compounds, for example as described herein.

General Styrenic Block Copolymers

In various embodiments, the compositions of the present invention include one or more styrenic block copolymers, in addition to the styrenic block copolymer having a controlled distribution copolymer block having a conjugated diene and a mono alkenyl arena. In a preferred embodiment, the styrenic block copolymers have a hard block (A) including aromatic vinyl or mono-alkenyl arena repeat units and at least one soft polymer bock (B) containing two or more repeat units, that are the same or different, and independently derived from olefin monomers. The styrenic block copolymer can be, for example, a triblock copolymer (A-B-A); or a tetrablock or higher multiblock copolymer. In a preferred embodiment, the styrenic block copolymer is a triblock copolymer (A-B-A) having two hard blocks.

The number average molecular weight and distribution of any type of styrenic block copolymer (SBC) described in this application are measured by gel permeation chromatography (GPO). The SBC is dissolved in a suitable solvent, such as THF, (typically 00001-0.010 wt %), and an appropriate quantity is injected into a GPO device. One suitable GPO device is available from Waters of Milford, Mass. as a Waters Breeze Dual Pump LC. The GPO analysis is performed at an appropriate elution rate (1 to 10 mL/min). The molecular weight distribution is characterized by the signals from UV and refractive index detectors, and number average molecular weights are calculated using a calibration curve generated from a series of narrow molecular weight distribution polystyrenes with peak molecular weights of 500 to 1,000,000 as standard.

Each hard polymer block (A) can have two or more same or different aromatic vinyl repeat units. For example, the block copolymer may contain (A) blocks which are styrene/alpha-methylstyrene copolymer blocks or styrene/butadiene random or tapered copolymer blocks so long as a majority of the repeat units of each hard block are aromatic vinyl repeat units. The (A) blocks are aromatic vinyl compound homopolymer blocks in one embodiment. The term “aromatic vinyl” is to include those of the benzene series, such as styrene and its analogs and homologs including o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, alpha-methylstyrene and other ring alkylated styrenes, particularly ring-methylated styrenes, and other monoalkenyl polycyclic aromatic compounds such as vinyl naphthalene, vinyl anthracene and the like. The preferred aromatic vinyl compounds are monovinyl monocyclic aromatics, such as styrene and alpha-methylstyrene, with styrene being most preferred. When three or more different repeat units are present in hard polymer block (A), the units can be combined in any form, such as random form, block form and tapered form.

Optionally, the hard polymer block (A) can comprise small amounts of structural units derived from other copolymerizable monomers in addition to the structural units derived from the aromatic vinyl compounds. The proportion of the structural units derived from other copolymerizable monomers is desirably 30% by weight or less and preferably 10% by weight or less based on the total weight of the hard polymer block (A). Examples of other copolymerizable monomers include, but are not limited to, 1-butene, pentene, hexene, conjugated dienes such as butadiene or isoprene, methyl vinyl ether, and other monomers.

The soft polymer block (B) of the styrenic block copolymer includes two or more same or different structural units. Soft polymer block (B) can be derived from olefin monomers generally having from 2 to about 12 carbon atoms and can include, for example, ethylene, propylene, butylene, isobutylene, etc. When the soft polymer block (B) has structural units derived from three or more repeat units, the structural units may be combined in any form such as random, tapered, block or any combination thereof. In one embodiment, the soft polymer block does not contain any unsaturated bonds.

In additional embodiments of the present invention, the styrenic block copolymer can have at least one soft polymer block (B) including two or more repeat units that are the same or different, independently derived from one or more of an olefin monomer and a diene monomer. When the diene monomer is present, the styrenic block copolymer is preferably hydrogenated or substantially hydrogenated. The conjugated diene monomers preferably contain from 4 to about 8 carbon atoms with examples including, but not limited to, 1,3-butadiene (butadiene), 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene (piperylene), 1,3-hexadiene, and the like. Therefore, in one embodiment, the soft polymer block (B) can have structural units derived from one or more of an olefin monomer(s) and diene monomer(s). As indicated hereinabove, when the soft polymer block (B) has structural units derived from three or more repeat units, the structural units may be combined in any form.

The styrenic block copolymers may be prepared utilizing bulk, solution or emulsion or other techniques as known in the art.

Optionally, the soft polymer block (B) can include small amounts of structural units derived from other copolymerizable monomers in addition to the structural units described. In this case, the proportion of the other copolymerizable monomers is generally 30% by weight or less, and preferably 10% by weight or less based on the total weight of the soft polymer block (B) of the styrenic block copolymer. Examples of other copolymerizable monomers include, for example, styrene, p-methylstyrene, α-methylstyrene, and other monomers that can undergo ionic polymerization.

Optionally, the styrenic block copolymer can be a functionalized styrenic block copolymer such as an acid or anhydride functionalized block copolymer, such as prepared by graft reacting an acid moiety or its derivative into the styrenic block copolymer via a free radically initiated reaction. Examples of suitable monomers which may be grafted include unsaturated mono and polycarboxylic acids and anhydrides containing from about 3 to about 10 carbon atoms. Examples of such monomers are fumaric acid, itaconic acid, citraconic acid, acrylic acid, maleic anhydride, itaconic anhydride, and citraconic anhydride, or the like. Suitable functionalized styrenic block copolymers generally contain from about 0.1 to about 10 percent by weight, preferably from about 0.2 to about 5 percent by weight of the grafted monomer, based on the total weight of the styrenic block copolymer. Grafting reactions can be carried out in solution or by melt mixing the base block copolymer and the acid/anhydride monomer in the presence of a free radial initiator, such as known in the art, see for example U.S. Pat. No. 6,653,408, herein fully incorporated by reference. Suitable functionalized block copolymers are available from KRATON Polymers, Kuraray, Asahi-Kasei, BASF and the like.

Styrenic block copolymers are available in the art from sources such as Kraton Polymers of Houston, Tex., as Kraton; Kuraray Co., Ltd. of Tokyo, Japan as SEPTON™ styrenic block copolymers, LCY Chemical Industry Corp, as Globalprene®, and TSRC Corporation of Taiwan as Taipol.

When present, the amount of the one or more styrenic block copolymers utilized in the compositions of the present invention ranges generally from about 1 to about 40 or 45 parts, desirably from about 10 to about 35 parts and preferably from about 10 or 15 to about 30 parts based on 100 parts by weight of the composition.

Controlled Distribution Copolymer Block-Containing Styrenic Block Copolymers

The controlled distribution block-containing styrenic block copolymers utilized in the invention have at least a first block of a mono alkenyl arene, such as styrene, and a second block of a controlled distribution copolymer of diene and mono alkenyl arene. Thus, the block copolymers can be any di-or higher block copolymers. In the case of a di-block copolymer composition copolymer, one block is an alkenyl arene-based block and polymerized therewith is a second block of the controlled distribution copolymer comprising diene and alkenyl arene. Tri-block or higher multi-block copolymers include at least one alkenyl arene-based block and at least one controlled distribution copolymer block comprising diene and alkenyl arene. In one preferred embodiment, the triblock-composition comprises, as end blocks, alkenyl arene-based blocks and a midblock of a controlled distribution copolymer comprising diene and alkenyl arene. Where a tri-block copolymer composition is prepared, the controlled distribution copolymer block can be designated as “B” and the alkenyl arene-based block designated as “A”. The A-B-A tri-block compositions can be made by either sequential polymerization or coupling. In one embodiment, in the sequential solution polymerization technique, the mono alkenyl arene is first introduced to produce a relatively hard aromatic-containing block, followed by introduction of the controlled distribution diene and alkenyl arene-containing mixture to form the midblock, and then followed by introduction of the mono alkenyl arena to form the terminal block.

In one embodiment, a method for making a controlled distribution copolymer block-containing styrenic block copolymer is set forth in U.S. Pat. No. 7,169,848 herein incorporated by reference. As utilized herein, “controlled distribution” is defined as referring to a molecular structure having the following attributes: (1) terminal regions adjacent to the mono alkenyl arene homopolymer (“A”) blocks that are rich in (i.e., having a greater than average amount of) conjugated diene units; (2) one or more regions not adjacent to the A blocks that are rich in (i.e., having a greater than average amount of) mono alkenyl arena units; and (3) an overall structure having relatively low blockiness. For the purposes hereof, “rich in” is defined as greater than the average amount, preferably greater than 5% the average amount. Prior to hydrogenation the styrene in the rubber block portion is copolymerized and incorporated in a controlled distribution having terminal regions that are rich in diene units (e.g. butadiene, isoprene, or a mixture thereof) and a center region that is rich in styrene units. Such polymers were hydrogenated under standard conditions such that greater than 95% of the diene double bonds in the rubbery block have been reduced. The process for producing a selectively hydrogenated styrene block copolymer is described in U.S. Pat. No. 7,169,848 to Bening at al.

The styrene blockiness is simply the percentage of blocky styrene to total styrene units:

Expressed thus, Polymer-Bd-S—(S)n-S-Bd-Polymer where n is greater than zero is defined to be blocky styrene. For example, if n equals 8 in the example above, then the blockiness index would be 80%. It is preferred that the blockiness index be less than about 40. For some polymers, having styrene contents of ten weight percent to forty weight percent, it is preferred that the blockiness index be less than about 10. In a preferred embodiment of the present invention, the subject controlled distribution copolymer block has two distinct types of regions—conjugated diene rich regions on the end of the block and a mono alkenyl arene rich region near the middle or center of the block. What is desired is a mono alkenyl arene-conjugated diene controlled distribution copolymer block, wherein the proportion of mono alkenyl arene units increases gradually to a maximum near the middle or center of the block and then decreases gradually until the polymer block is fully polymerized.

The alkenyl arena can be styrene, alpha-methylstryene, para-methylstyrene, vinyl toluene, vinylnaphthalene, or para-butyl styrene or mixtures thereof. Of these, styrene is most preferred and is commercially available, and relatively inexpensive, from a variety of manufacturers. The conjugated dienes for use herein comprise 1,3-butadiene and substituted butadienes such as isoprene, piperylene, 2,3-dimethyl-1,3-butadiene and 1-phenyl-1,3-butadiene, or mixtures thereof. Of these, 1,3-butadiene is most preferred.

For the controlled distribution or B block the weight percent of mono alkenyl arena in each B block is between about 10 weight percent and about 75 weight percent, preferably between about 25 weight percent and about 50 weight percent for selectively hydrogenated polymers.

It is preferred that, to ensure significantly elastomeric performance while maintaining desirably high Tg and strength properties, as well as desirable transparency, the tri block and multi-block polymer's alkenyl arene content is greater than about 20% weight, preferably from about 20% to about 80% weight. This means that essentially all of the remaining content, which is part of the diene/alkenyl arena block, is diene. It is also important to control the molecular weight of the various blocks. For an AB diblock, desired block weights are 3,000 to about 60,000 for the monoalkenyl arene A block, and 30,000 to about 300,000 for the controlled distribution conjugated diene/mono alkenyl arena B block. Preferred ranges are 5,000 to 45,000 for the A block and 50,000 to about 250,000 for the B block. For the triblock, which may be a sequential ABA or coupled (AB)2X block copolymer, the A blocks should be 3,000 to about 60,000 preferably 5,000 to about 45,000, while the B block for the sequential block should be about 30,000 to about 300,000 and the B blocks (two) for the coupled polymer half that amount. The total average molecular weight for the triblock copolymer should be from about 40,000 to about 400,000 and for the radial copolymer from about 60,000 to about 600,000. For the tetrablock copolymer ABAB the block size for the terminal B block should be about 2,000 to about 40,000, and the other blocks may be similar to that of the sequential triblock copolymer. These molecular weights are most accurately determined by light scattering measurements, and are expressed as number average molecular weight.

The controlled distribution block copolymer can be hydrogenated in various embodiments. One preferred hydrogenation is selective hydrogenation of the diene portions of the final block copolymer alternatively both the “B” blocks and the “A” blocks may be hydrogenated, or merely a portion of the “B” blocks may be hydrogenated.

Hydrogenation can be carried out via any of the several hydrogenation or selective hydrogenation processes known in the prior art. For example, such hydrogenation has been accomplished using methods such as those taught in, for example, U.S. Pat. Nos. 3,595,942; 3,634,549; 3,670,054; 3,700,633; and Re. No. 27,145, the disclosures of which are incorporated herein by reference. These methods operate to hydrogenate polymers containing aromatic or ethylenic unsaturation and are based upon operation of a suitable catalyst. Such catalyst, or catalyst precursor, preferably comprises a Group VIII metal such as nickel or cobalt which is combined with a suitable reducing agent such as an aluminum alkyl or hydride of a metal selected from Groups I-A, II-A, AND III-B of the Periodic Table of the Elements, particularly lithium, magnesium or aluminum. This preparation can be accomplished in a suitable solvent or diluent at a temperature from about 20° C. to about 80° C. Other catalysts that are useful include titanium based catalyst systems. Hydrogenation can be carded out under such conditions that at least about 90 percent of the conjugated diene double bonds have been reduced, and between zero and 10 percent of the arena double bonds have been reduced. Preferred ranges are at least about 95 percent of the conjugated diene double bonds reduced, and more preferably about 98 percent of the conjugated diene double bonds are reduced. Alternatively, it is possible to hydrogenate the polymer such that aromatic unsaturation is also reduced beyond the 10 percent level mentioned above. Such exhaustive hydrogenation is usually achieved at higher temperatures. In that case, the double bonds of both the conjugated diene and arene may be reduced by 90 percent or more.

In an alternative, the block copolymer of the present invention may be functionalized in a number of ways. One way is by treatment with an unsaturated monomer having one or more functional groups or theft derivatives, such as carboxylic acid groups and their salts, anhydrides, esters, imide groups, amide groups, and acid chlorides. The preferred monomers to be grafted onto the block copolymers are maleic anhydride, maleic acid, fumaric acid, and their derivatives. A further description of functionalizing such block copolymers can be found in Gergen et al, U.S. Pat. No. 4,578,429 and in U.S. Pat. No. 5,506,299. In another manner, the selectively hydrogenated block copolymer of the present invention may be functionalized by grafting silicon or boron containing compounds to the polymer as taught in U.S. Pat. No. 4,882,384. In still another manner, the block copolymer of the present invention may be contacted with an alkoxy-silane compound to form silane-modified block copolymer. In yet another manner, the block copolymer of the present invention may be functionalized by grafting at least one ethylene oxide molecule to the polymer as taught in U.S. Pat. No. 4,898,914, or by reacting the polymer with carbon dioxide as taught in U.S. Pat. No. 4,970,265. Still further, the block copolymers of the present invention may be metallated as taught in U.S. Pat. Nos. 5,208,300 and 5,276,101, wherein the polymer is contacted with an alkali metal alkyl, such as a lithium alkyl. And still further, the block copolymers of the present invention may be functionalized by grafting sulfonic groups to the polymer as taught in U.S. Pat. No. 5,516,831. All of the patents mentioned in this paragraph are incorporated by reference into this application.

In various embodiments of the invention, the mono alkenyl arene is present in a total weight in an amount of greater than 20% and preferably greater than 35% based on the total weight of the controlled distribution block copolymer. In various embodiments the soft or B block of the controlled distribution copolymer block has a mono alkenyl arena content of less than 30%, desirably less than 29% by weight. The controlled distribution block copolymer of the present invention may include the copolymers sold under the trade name Kraton A® by Kraton Polymers, Kraton A1536 and A1535 are examples.

In various embodiments of the invention, the controlled distribution block-containing styrenic block copolymers are utilized in compositions of the present invention in an amount from about 5 to about 90 parts, desirably from about 10 or about 15 to about 70 or 80 parts, and preferably from about 20 to about 30 or 35 parts based on 100 parts by weight of the composition.

High Molecular weight Styrenic Block Copolymers.

In some embodiments of the present invention, the compositions include one or more relatively high molecular weight styrenic block copolymers. High molecular weight as utilized herein refers to those block copolymers having a number average molecular weight generally greater than 300,000 g/mol. The high molecular weight styrenic block copolymers have been found to reduce gloss, improve physical strength and elasticity, increase melt strength, improve processibility, especially in extrusion applications, and to reduce softener or vegetable oil bleeding in various compositions of the present invention including biorenewable content.

in one embodiment, tri-block styrenic block copolymers are preferred with the copolymers having styrene end blocks with average block length greater than 50,000 and a butadiene mid-block greater than 200,000. Such copolymers can be made from sequential anionic living polymerization. In one embodiment, the high molecular weight styrenic block copolymers are substantially fully hydrogenated. High molecular weight styrenic block copolymers are available from Kraton as Kraton 1633, Kuraray as Septon 4099 and TSRC as Taipol 6159.

When present in a composition of the present invention, the high molecular weight styrenic block copolymer is utilized in an amount generally from about 1 to about 30, desirably from about 2 to about 20 and preferably from about 3 to about 15 parts by weight based on 100 total parts by weight of the composition.

The composition of the present invention includes at least one or at least two biorenewable components, preferably at least one biorenewable softener and at least one biorenewable additive in various embodiments.

As indicated hereinabove, one of the biorenewable components is a softener preferably an oil, e.g. natural oil, such as an ester group-containing oil, such as a monoester, diester, or triester. As defined in the art, an ester comprises the formula R—COO—R1, wherein R is hydrogen or a hydrocarbyl and R1is a hydrocarbyl, e.g. an alkyl, aryl, or alkyl aryl, each optionally substituted.

In one preferred embodiment, the biorenewable softener component comprises a glyceride or acylglycerol, i.e. a monoglyceride, diglyceride, triglyceride, or combination thereof. Many naturally occurring fats and oils are the fatty acid esters of glycerol. Triglycerides are preferred in one embodiment. The glycerides can be saturated or unsaturated or a combination thereof. The styrenic block copolymers having a controlled distribution copolymer block including a conjugated diene and a mono alkenyl arena are less polar than a styrenic block copolymer containing a random conjugated diene and mono alkenyl arene block. Thus, it is expected that such block copolymers are miscible with standard mineral or white oil. However, it was surprisingly discovered that such controlled distribution copolymer block-containing styrenic block copolymers can be formulated with relatively high amounts of biorenewable softeners.

One or more esters can be employed in the present invention. In a preferred embodiment at least one ester utilized is biorenewable. Suitable esters that can be employed in the present invention include those of the following formulas:

where n has any value from 1 to about 8, and R1and R2are the same or different and are hydrogen or a hydrocarbyl (including substituted hydrocarbyls) provided the ester is compatible in the compositions of the invention. It is noted that a suitable group for R2depends on the value of n.

In one embodiment of the present invention, n is 1, and the ester has the formula R1C(O)OR2where R1is a C10-C22, preferably a C5-C22, alkyl, and R2is a lower alkyl radical containing from 1 to 22 carbon atoms. R1is preferably C13or more when SEEPS is present in a composition.

Another class of suitable esters that may be employed in the present invention is represented by the following formula:

where R1is defined above and R3includes alkylene or substituted alkylene.

Still another class of suitable esters that may be employed in the present invention is represented by the following formula:

where R4, R5, and R6individually include alkylene or substituted alkylene; and R7, R8, and R9individually include hydrogen or a hydrocarbyl.

In a preferred embodiment, the ester-containing oils are natural product oils that are typically found in animal or plant tissues, including those which have been hydrogenated to eliminate or reduce unsaturation. These natural product oils that can be employed in the present invention include compounds that have the following formula:

where R10R11and R12may be the same or different fatty acid radicals containing from 8 to 22 carbon atoms.

The amount of softener or ester, preferably biorenewable ester-containing oils, present in the thermoplastic elastomer compositions of the present invention can vary depending upon the types of polymers utilized and end products desired to be formed with the compositions. That said, in one embodiment, the amount of softener, preferably biorenewable, utilized in the thermoplastic elastomer compositions ranges generally from about 5 to about 400 parts, desirably from about 50 to about 250 parts, and preferably from about 75 or 100 to about 200 parts by weight based on 100 total parts by weight of totals styrenic block copolymer. In another embodiment, the softener or ester, preferably biorenewable, ranges in an amount generally from about 1 to about $5 parts, desirably from about 5 to about 75 parts, and preferably from about 10 to 65 about parts by weight based on 100 total parts by weight of the composition.

Still additional softeners or extenders include fatty ethers, fatty alcohols and fatty amines. Said components, individually, can be utilized in amounts set forth for the softeners or esters hereinabove.

Fatty Ethers

Fatty ethers are utilized in some compositions of the present invention. Fatty ethers having the general formula R13—O—R14, can be utilized wherein R13contains from about 6 to about 34 carbon atoms and preferably from about 10 to about 22 carbon atoms, and R4contains from about 1 to about 22 carbon atoms and preferably from about 4 to about 22 carbon atoms. The fatty ethers can be linear or branched.

Fatty Alcohols

Fatty alcohols are utilized in some compositions of the present invention. Fatty alcohols having the general formula R15—OH, can be utilized wherein R15contains from about 6 to about 34 carbon atoms and preferably from about 13 to about 34 carbon atoms. Examples of fatty alcohols include, but are not limited to 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tridecanol, 1-tetradecanol 1-pentadecanol, 1-hexadecanol, 1-heptadecanol, 1-octadecanol, 1-nonadecanol, 1-eicosanol, 1-heneicosanol, 1-docosanol, 1-tricosanol, 1-tetracosanol, 1-pentacosanol, 1-hexacosanol, 1-heptacosanol, 1-octasanol, 1-nonacosanol, 1-tricontanol, 1-hentriacontanol, 1-dotriacontanol, 1-tritriacontanol, and 1-tetratriacontanol. In one embodiment, at least one fatty alcohol utilized includes saturation and branching. The fatty alcohols can be linear or branched, for example Guerbet alcohols.

Fatty Amines

Fatty amines are utilized in some compositions of the present invention. Fatty amines can be utilized having the general formula:

wherein each R16, R17and R18, independently, is hydrogen, or contains from about 4 to about 34 carbon atoms and preferably from about 10 to about 22 carbon atoms, with the proviso that at least one said R is not hydrogen. Examples of suitable fatty amines include, but are not limited to, amines derived from fatty acids, for example, dimethyl stearamine, stearyl amine, and oleyl amine. In one embodiment at least one fatty amine utilized includes saturation and branching. The fatty amines can be linear or branched.

As indicated hereinabove, the compositions of the present invention also include a synergistic additive that is believed to create greater stability within the thermoplastic elastomer compositions. Some biorenewable synergistic additives are polar components in various embodiments. The polar synergistic additive can provide one or more of better oil retention at room temperature and at higher temperatures and in some embodiments, greater tensile strength, tensile modulus at various percentages, tensile elongation and tear strength when compared to a corresponding composition without the additive. The thermoplastic elastomer compositions of the present invention can be processed in standard processing equipment such as injection molders and extruders.

A number of different biorenewable synergistic additives can be utilized in combination with the biorenewable softeners of the present invention. For example, additives include, but are not limited to, starches; thermoplastic starches; and biorenewable polar polymers such as aliphatic polyesters, e.g. polylactic acids and polylactides.

Starch

In one embodiment, starches and/or starch-containing components are utilized as a biorenewable synergistic additive. Starch-containing components as utilized herein refer to a composition comprising at least starch and preferably a dispersion aid, for example glycerin. For example, in one embodiment of a dry blend process, if starch is used, a dispersion aid such as glycerin is added to provide desired dispersion of the starch in the blend.

The effective plasticizer or dispersion aid helps swell and break the crystalline starch granule, and helps lubricate newly exfoliated, amorphous crystalline starch segments to obtain the thermoplastic starch. Heat and shear further aids in the starch gelatinization process. The plasticizer or dispersion aid can include polyols, such as glycerol, sorbitol etc., adipic acid derivatives, such as tridecyl adipate, benzoic acid derivatives, such as isodecyl benzoate, citric acid derivatives, such as tributyl citrate, glycerol derivatives, phosphoric acid derivatives, such as tributyl phosphate, polyesters, sebacic acid derivatives, dimethyl sebacate, urea. The plasticizer or dispersion aid can also be selected from one or more of glycerine, ethylene glycol, propylene glycol, ethylene diglycol, ethylene triglycol, propylene triglycol, polyethylene glycol, polypropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,2,6-hexanetriol, 1,3,5-hexanetriol, neopentyl glycol, trimethylol propane, pantaerythritol, and the acetate, ethoxylate, and propoxylate derivatives thereof. Moreover, the plasticizer or dispersion aid can be selected from one or more of sorbitol ethoxylate, glycerol ethoxylate, pentaerythritol ethoxylate, sorbitol acetate, and pentaerythritol acetate.

Starches and starch-containing components provide improved softener stability. In various embodiments with other biorenewable components, for example PLA, compositions having desired hardness ranges can be achieved. Starches and starch-containing components further increase bio-renewable content of the compositions in addition to the biorenewable content of the compositions derived from the softener or plasticizer, without significant deterioration of the mechanical properties of the compositions.

Starch includes modified starches, such as chemically treated and cross-linked starches, and starches in which the hydroxyl groups have been substituted with organic acids, to provide esters or with organic alcohols to provide ethers, with degrees of substitution in the range 0-3.

Starch also includes extended starches, such as those extended with proteins; for example with soya protein.

Thermoplastic Starch

The biorenewable additives of the present invention also include thermoplastic starches. Thermoplastic starches offer the advantages of the capability of flow and are thus suitable for use in polymer processing methods and equipment. Thermoplastic starches are available from various commercial sources in compounded form. In various embodiments, thermoplastic starches are prepared and used simultaneously in a compounding process to form compositions of the present invention. Methods of preparing thermoplastic starch are disclosed in U.S. Pat. No. 6,605,657, herein incorporated by reference. In various embodiments of the present invention a dry blended mixture of elastomer such as styrenic block copolymer, thermoplastic and softener together with other processing additives are fed through an extruder. The mixture is then melt mixed with the thermoplastic starch in the remaining downstream portion of the extruder. There are two extruders involved in this operation. The two are connected in a “T” shape.

When present in compositions of the present invention, the total starch, one or more of starch and thermoplastic starch, is in an amount from about 2 to about 40 or 80, desirably from about 2 to about 60 and preferably from 2 to about 40 parts by weight based on 100 total parts by weight of the composition. When utilized, the dispersion aid is present in an amount from about 1 to about 80, desirably from about 2 to about 60 and preferably from 2 to about 50 parts by weight based on 100 parts of the starch.

Polar Polymer

The polar polymers are provided in amounts which impart desirable properties to the thermoplastic elastomer compositions of the invention, and, when present, generally range in an amount from about 0.1 or 1 to about 80 parts, desirably from about 2 to about 60 parts, and preferably from about 2 or 3 to about 20 or 40 parts based on 100 total parts by weight of the composition of the present invention.

In one embodiment, the compositions of the present invention optionally include one or more polyolefins, which as utilized herein are defined as one or more of a polyolefin polymer and a polyolefin copolymer unless otherwise indicated. Polyolefins suitable for use in the compositions of the present invention comprise amorphous or crystalline homopolymers or copolymers of two or more same or different monomers derived from alpha-monoolefins having from 2 to about 12 carbon atoms, and preferably from 2 to about 8 carbon atoms. Examples of suitable olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, and combinations thereof. Polyolefins include, but are not limited to, low-density polyethylene, high-density polyethylene, linear-low-density polyethylene, polypropylene (isotactic and syndiotactic), ethylene/propylene copolymers, and polybutene. Polyolefin copolymers can also include the greater part by weight of one or more olefin monomers and a lesser amount of one or more non-olefin monomers such as vinyl monomers including vinyl acetate, or a diene monomer, etc. Polar polyolefin polymers include ethylene acrylate and ethylene vinyl acetate, for example. In a preferred embodiment, EVA is utilized that has a vinyl acetate content of greater than 5 percent. Generally, a polyolefin copolymer includes less than 40 weight percent of a non-olefin monomer, desirably less than 30 weight percent, and preferably less than about 10 weight percent of a non-olefin monomer.

In a further embodiment, the polyolefin can include at least one functional group per chain or can be a blend of non-functionalized polyolefins and functionalized polyolefins. Functional groups can be incorporated into the polyolefin by the inclusion of for example, one or more non-olefin monomers during polymerization of the polyolefin. Examples of functional groups include, but are not limited to, anhydride groups such as maleic anhydride, itaconic anhydride and citraconic anhydride; acrylates such as glycidyl methacrylate; acid groups such as fumaric acid, itaconic acid, citraconic acid and acrylic acid; epoxy functional groups; and amine functional groups. Functional group-containing polyolefins and methods for forming the same are well known to those of ordinary skill in the art. Functionalized polyolefins are available commercially from sources such as Uniroyal, Atofina, and DuPont. Epoxy modified polyethylenes are available from Atofina as LOTADER®. Acid modified polyethylenes are available from DuPont as FUSABOND®.

Polyolefin polymers and copolymers are commercially available from sources including, but not limited to, Chevron, Dow Chemical, DuPont, ExxonMobil, Huntsman Polymers, Ticona and Westlake Polymer under various designations.

When present, the polyolefins range in an amount generally from about 0.5 to about 60 parts, desirably from about 0.5 or 2 to about 30 or 50 parts, and preferably from about 0.5 to about 20 or 40 parts by weight based on 100 total parts by weight of the total composition.

Additives

The compositions of the present invention may include additional additives including, but not limited to lubricants, light stabilizers, antioxidant, flame retardant additives, pigments, peroxides, heat stabilizers, processing aids, mold release agents, flow enhancing agents, nanoparticles, foam agents, platelet fillers and non-platelet fillers. Examples of fillers for use in the compositions include, but are not limited to, one or more of calcium carbonate, talc, clay, zeolite, silica, titanium dioxide, carbon black, barium sulfate, mica, glass fibers, whiskers, carbon fibers, magnesium carbonate, glass powders, metal powders, kaolin, graphite, and molybdenum disulfide. Suitable fillers include bio-based fillers, e.g. various fibers, cellulose, and/or lignin.

Other Polymers

In various embodiments, other polymers can be added to the compositions of the present invention in an assortment of amounts provided that such polymers do not interfere with the desired performance of the compositions and constructions formed therewith. Examples of additional polymers include, but are not limited to, polyamide such as nylon, acrylonitrile-butadiene-styrene copolymers (ABS), halogenated polymers such as polyvinyl chloride, polycarbonates, acrylic polymers, PET, PBT, TPU (including TPU with a bio based polyester block), polyether-block-amide (PEBA).

The high biorenewable content thermoplastic elastomer compositions of the present invention can be formed by blending the desired components in one or more steps, preferably by mixing. The composition is preferably heated to obtain a melted composition, preferably with mixing, to substantially disperse the components thereof. Melt blending is performed at a temperature generally from about 150° C. to about 250° C. and preferably from about 170° C. to about 210° C. The compositions can be prepared for example in a Banbury, on a two roll mill, in a continuous mixer such as a single screw or twin screw extruder, a kneader, or any other mixing machine as known to those of ordinary skill in the art. The compositions containing thermoplastic starch are prepared in a one step process using combination of single screw extruder connected midway to a twin screw extruder. The process is described in detail in U.S. Pat. No. 6,844,380 herein fully incorporated by reference. After preparation of the compositions, they can be pelletized or diced utilizing appropriate equipment, if desired for future further processing. Alternatively, the compositions can be directly molded, or shaped as desired for example using an extruder, injection molder, compression molder, calender, or the like.

As described herein, desirable compositions can be formed utilizing the teachings of the present invention which exhibit high oil stability; low oil softener or ester leaching; or low oil, etc., bleeding. Oil stability or the like is defined in one embodiment according to the present invention utilizing a loop spew test as defined with the examples section. Desirable compositions according to the present invention have a loop spew rating of 2 or less, desirably 1 or less, and preferably 0, that is no visible evidence of oil on the loop surface.

The compositions of the present invention can be utilized to form a variety of articles or parts of articles such as, but not limited to, shaving razors, toothbrushes, writing utensils such as pens or pencils, brushes such as paint brushes and her brushes, hair dryers, tools, for example screwdrivers, hammers, wrenches, pliers and saws, kitchen appliances, for example handles for refrigerators, ovens, microwaves, dishwashers, kitchen utensils, such as spoons, forks, knives, spatulas, can openers, bottle openers, corkscrews, whisks and vegetable peelers, vacuum cleaner handles, brooms, mops, rakes, shovels, scissors, sporting equipment, such as fishing poles, firearms, tennis rackets, and golf clubs, bracelets for example for absorbing sweat, various seals including automotive weather seals, window encapsulation. The thermoplastic elastomer compositions of the invention can also be coated on fabric, such as making wet grip gloves, non-skid fabrics, etc.

The compositions of the present invention may be formed as a composite with a different substrate for example by connecting the composition of the present invention to the substrate utilizing any desired method, for example overmolding, insert molding, coextrusion, welding or bonding with an adhesive. Overmolding generally involves bonding the thermoplastic elastomer composition to a polymeric substrate utilizing a two-shot or multi-shot injection molding process or a co-injection molding process. Overmolding generally includes providing two or more different materials that are injected into the same mold during the same molding cycle. Insert molding generally comprises inserting pre-molded or preformed substrate into a mold and the composition of the present invention is molded directly over or to at least a portion of the insert.

FIG. 1illustrates one embodiment of a composite10which comprises a layer20including a thermoplastic elastomer composition having biorenewable content of the present invention connected to a substrate30. The substrate can be, for example, one or more of a polymer, rubber or other elastomer, glass, metal or natural substrate, such as wood.FIG. 2illustrates a writing utensil40having a grip50formed comprising a composition of the present invention including biorenewable content. Grip50is connected to body60, in particular formed in the shape of a pen.

For the avoidance of doubt, the compositions of the present invention encompass all possible combinations of the components, including various ranges of said components, disclosed herein.

EXAMPLES

The examples set forth below are provided to illustrate the high biorenewable content thermoplastic elastomer compositions of the present invention. These examples are not intended to limit the scope of the invention.

All formulations were prepared in a Leistriz 30 mm intermeshing co-rotating twin screw extruder with L/D ratio of 40:1. All ingredients were premixed to a uniform, free-flowing state and then fed to the main feed throat. The extrusion temperature was 170-200° C. and the extruder screw speed was 180-350 RPM. Samples from the twin screw extruder were then injection molded at 170-190° C. into plaques approximately 2 mm thick, 6.0 cm wide by 8.75 cm long.

The oil stability in the compounded TPE was tested with a method modified from ASTM D 3291, which was designed for testing plasticizer stability in PVC compound. An approximately 2.54 cm×815 cm specimen was cut from an approximately 2 mm thick molded plaque. The test specimen was conditioned for a minimum of 20 hours at 23° C. A line having a width of about 0.5 mm is drawn in the middle of the specimen along the long direction of the specimen using a ballpoint pen. The conditioned specimen was placed in the loop holder so that a 1.27 cm loop was formed from the edge of the clamp to the inner edge of the loop, with tolerance being +/−0.159 cm. The clamped specimen was conditioned for 24 hrs at 23° C., or other temperature as specified within a specific example. The specimen was removed from the clamp, examined, and rated as follows:

LoopSpewAmount of OilRatingExudationComment0NoneNo visible evidence of oil in the loop surface1Very SlightVery slight sign of oil appears near the creaseline, ball-point line stays sharp, and cannot berubbed off2SlightSlight sign of oil appears uniformly in the loop,line stays sharp but starts to widen3ModerateModerate oil uniformly appears in the loop.Line further widens and can be rubbed off4SevereSome areas have oil drop, some part of theline starts to disappear5Heavy/Heavy oil dripping, line has mostly disappearedDripping

The following raw materials were utilized for the examples.

As shown in Table 1, Comparative #1 is a general purpose TPE based on regular SBC and white mineral oil, Comparative #2 is based on a controlled distribution block-containing SEES and mineral oil, and Comparative #3 on a controlled distribution block-containing SEES with vegetable oil, and both Comparatives #2 and #3 showed noticeable oil spew. With the use of high MW SBC, and some polar polymer, PLA, the oil stability is much improved at equivalent hardness as illustrated in Example #1.

In Table 2, Comparative #4 showed substantial oil bleeding. Examples #2 and #3 with either TPS or starch with glycerin as a dispersion aid exhibited greatly improved oil stability.

In Table 3, Comparative #5 showed substantial oil bleeding. Examples #4 and #5 with a polar polymer, PLA, improved the oil stability, but reduced hardness/strength. Examples #6 & 7 showed improved oil stability and strength while maintaining hardness with the use of high MW SBC, high MW PP in addition to PLA or EVA.

In Table 4, Comparative #6 showed substantial oil bleeding. Example #8 showed some oil stability improvement with the use of relatively high MW SBC. Examples #9 and #10 with the polar polymer PLA improved the oil stability, but reduced hardness/strength. Examples #11 and #12 showed improved oil stability and strength while maintaining hardness with the use of high MW SBC, high MW PP in addition to PLA or EVA.

In Table 5, Comparative #7 exhibited substantial oil bleeding. The addition of a polar biopolymer, namely PLA, and high MW SBC significantly improved oil stability. Replacing a portion of the soybean oil with an ester-containing oil having relatively low polyunsaturation such as high oleic acid sunflower oil improved oil compatibility and heat stability, see Example 14. Replacing the soybean oil with an ester-containing oil having low-polyunsaturation, namely the high oleic acid sunflower oil also improved the oil compatibility and heat stability, see Example #15, as compared to Comparative #7. Example #16 including a combination of ester-containing oils, namely a high oleic acid sunflower oil and hydrogenated soybean oil exhibited the best bio-compatibility and heat stability between Examples 13 through 16.

While in accordance with the patent statutes the best mode and preferred embodiment have been set forth, the scope of the invention is not intended to be limited thereto, but only by the scope of the attached claims.