Thermoplastic Elastomer Gel

Abstract

A thermoplastic elastomer (TPE) compound is disclosed, which has a very low hardness due to the use of a combination of a high styrene content styrene-ethylene-ethylene-propylene-styrene copolymer, a conventional styrene-ethylene-ethylene-propylene-styrene copolymer, and a plasticizer. Ultra-soft extruded or molded plastic articles can be formed from pellets of the compound, with a resulting Shore OO hardness of about 35 to about 52. The molded articles can be prepared using injection molding techniques.

Description

[0001] Claiming priority

[0002] This application claims the benefit of priority to U.S. Provisional Application Serial No. 62 / 839,434, filed on April 26, 2019, with Attorney Docket No. 12019011, which is incorporated herein by reference in its entirety. Field of the Invention

[0003] The present invention relates to thermoplastic elastomers, and in particular to gel-like elastomeric materials. Background of the Invention

[0005] Thermoplastic elastomeric gels based on styrenic block copolymers and oils are well known and used in a variety of applications including, but not limited to, vibration reduction, pressure reduction, cushioning, gripping, therapeutic and orthopedic devices, etc. However, there is a need for an improved thermoplastic elastomeric gel compound having good viscosity, hardness and compression set physical properties. SUMMARY OF THE INVENTION

[0007] The present technology relates to thermoplastic elastomer gel compounds.

[0008] The thermoplastic elastomer gel compound of the present technology may include a high styrene content styrene-ethylene-ethylene-propylene-styrene copolymer, a conventional styrene-ethylene-ethylene-propylene-styrene copolymer; and a plasticizer. In one embodiment, the compound may include optional additives.

[0009] In one aspect, the present technology discloses a method of injection molding a thermoplastic gel compound into a desired shape.

[0010] Thermoplastic elastomer gel compounds of the present technology can have good viscosity, hardness and compression set physical properties.

[0011] Features of the present invention will become apparent with reference to the following embodiments. DETAILED DESCRIPTION

[0012] In some embodiments, the present invention is directed to thermoplastic compounds.

[0013] In some embodiments, the present invention is directed to thermoplastic articles.

[0014] In other embodiments, the present invention is directed to methods of making thermoplastic articles.

[0015] Required and optional features of these and other embodiments of the invention are described below.

[0016] As used herein, the term "compound" refers to a composition or mixture formed by melt mixing or compounding a neat polymer resin and at least one other ingredient including, but not limited to, one or more additives and / or one or more other polymer resins.

[0017] As used herein, the term "formed from" (including related terms, such as "formed"), with respect to an article (or a component of an article) and a thermoplastic material, means that the article (or a component of an article) is extruded, molded, shaped, pressed, or otherwise made from a thermoplastic material under sufficient heating to achieve such formation. Thus, in some embodiments, the term "formed from" (including related terms, such as "formed") means that the article (or a component of an article) may include, consist essentially of, or consist of the material; and, in other embodiments, the article (or a component of an article) consists of the material because the article (or a component of an article) is made, for example, by an extrusion process or a molding process.

[0018] As used herein, in some embodiments, the term "free of" a certain ingredient or substance means that the amount of the component or substance is not present in an intentional manner, and in other embodiments, the term means that a functionally effective amount of the ingredient or substance is not present, and in other embodiments, the term means that the amount of the component or substance is not present.

[0019] As used herein, the term "hardness" refers to the hardness of a specimen measured according to ASTM D 2240. Unless expressly specified otherwise, hardness is reported as Shore OO hardness.

[0020] The present technology provides a thermoplastic elastomer gel suitable for consumer applications requiring soft gel products (e.g., cushions). The thermoplastic elastomer gel ("gel compound") may include a styrene block polymer, a plasticizer, and optional additives. Each of these ingredients may include one or more different components. For example, in one embodiment, the styrene block polymer may include at least two different styrenic block copolymers, for example, a high styrene content styrene-ethylene-ethylene-propylene-styrene polymer and a conventional styrene-ethylene-ethylene-propylene-styrene polymer. The gel compound may not include all of the above components. The gel compound may include other components in addition to the above components.

[0021] The gel compound has many advantages over currently commercially available gel compounds, including but not limited to improved softness, improved elasticity, and improved processability.

[0022] Styrene block copolymers

[0023] The gel compound may include a styrenic block copolymer ("SBC"). One specific SBC that may be used in this technology is a styrene-ethylene-ethylene-propylene-styrene (SEEPS) polymer. SEEP polymers are hydrogenated diblock and triblock styrene copolymers that are capable of exhibiting rubber-like properties over a wide temperature range. SEEP polymers exhibit many physical properties useful in this technology, including but not limited to improved tensile strength and resistance to environmental factors. SEEP polymers are recyclable thermoplastic elastomers. In the presence of heat and shear during processing, the polystyrene domains soften and allow them to flow.

[0024] There are many types of SEEPS polymers that can provide different benefits to the final composition. For example, the gel compound of the present application may include a hydrogenated SEEPS copolymer ("high styrene content SEEPS copolymer") with a high styrene content (e.g., a styrene content>35% by weight). The high styrene content SEEPS copolymer may have a large molecular weight, such as a weight average molecular weight of approximately 250,000 to 350,000, which in turn provides the molecular weight for the gel compound. The large molecular weight will allow for good compression set of the final gel compound and allow for improved fluidity, lower viscosity, and rapid solidification in the melt. A non-limiting example of a high styrene content SEEPS copolymer that can be used in the present technology is Septon TM J3341. As described in U.S. Patent No. 9,831,655, Septon TM The J3341 copolymer is an exemplary star copolymer, meaning it has several linear chains attached to a central core, so its compact structure, high arm density, and large molecular weight provide good compression set and other desirable characteristics for the final product. In one embodiment, the gel compound may include one or more high styrene content SEEPS copolymers. In one embodiment, the gel compound may include one or more conventional styrene content SEEPS copolymers.

[0025] The gel compound may also include a conventional hydrogenated SEEPS triblock copolymer, i.e., a SEEPS triblock copolymer having a styrene content of less than 35% ("conventional SEEPS copolymer"). In one embodiment, the weight average molecular weight of the conventional SEEPS copolymer is from 100,000 to 350,000. Conventional SEEPS copolymers may have a lower molecular weight than high styrene content SEEPS copolymers. Examples of such conventional SEEPS polymers include, but are not limited to, Septon TM 4000 series, such as Septon TM 4055、Septon TM4044 and Septon TM 4033. In one embodiment, the gel compound may include a conventional SEEPS copolymer. In one embodiment, the gel compound may include more than one conventional SEEPS copolymer. In one embodiment, the conventional SEEPS copolymer may have a medium molecular weight, such as Septon TM 4044.

[0026] In one aspect, the high molecular weight conventional SEEPS copolymer can have a weight average molecular weight of 250,000 to 350,000. In one aspect, the medium molecular weight conventional SEEPS copolymer can have a weight average molecular weight of about 150,000 to about 250,000. In one aspect, the low molecular weight conventional SEEPS copolymer has a weight average molecular weight of 50,000 to 150,000. In one aspect, Septon TM 4055 is an exemplary high molecular weight SEEPS copolymer. In one aspect, Septon TM 4044 is an exemplary medium molecular weight SEEPS copolymer. In one aspect, Septon TM 4033 is an exemplary low molecular weight SEEPS copolymer.

[0027] SEEPS copolymers with high styrene content, such as Septon TM J3341, can provide characteristic low compression set and softness. However, due to the high molecular weight and styrene content, even if the overall viscosity is low, the molecular rearrangement (set up) is very fast in the molding process, especially in the conventional molding process, which may lead to processing difficulties and aesthetic problems of the final molded part. Conventional SEEPS copolymers may not provide the required good compression set and good flow performance balance for gel, whether it is a balance of low compression set and high viscosity or high compression set and low viscosity. Adding conventional SEEPS copolymers to high styrene content SEEPS copolymer compounds may modify the compound. In doing so, people have obtained unexpected results, and the resulting compound shows all required properties, i.e. a good balance of low compression set and low viscosity.

[0028] The amounts of SEEPS copolymers (high styrene and conventional) can be provided in any suitable ratio, including but not limited to 90:10 high styrene content SEEPS copolymer:conventional SEEPS copolymer; 80:20 high styrene content SEEPS copolymer:conventional SEEPS copolymer; 70:30 high styrene content SEEPS copolymer:conventional SEEPS copolymer; 60:40 high styrene content SEEPS copolymer:conventional SEEPS copolymer; or even 50:50 high styrene content SEEPS copolymer:conventional SEEPS copolymer.

[0029] The amount of SEEPS copolymer in the compound (i.e., the total amount of the high styrene content copolymer and the conventional copolymer) can be any suitable amount, including but not limited to 20-120 parts by weight of the gel compound; 40-100 parts by weight of the gel compound; and 60-80 parts by weight of the gel compound.

[0030] Plasticizing oil

[0031] Any conventional plasticizer, preferably paraffin oil, is suitable for use in the present technology. Plasticizers can be used, for example, to adjust the softness and / or improve the flow properties or other properties of thermoplastic elastomer gel compounds. Any conventional oil that can plasticize styrenic block copolymers, such as mineral oil, vegetable oil, synthetic oil, etc., can be used in the present invention. Examples of commercially available oils include: PURETOL TM 380 oil obtained from Petro-Canada; and PRIMOL TM 382 Trade name oil obtained from ExxonMobil.

[0032] In some embodiments, plasticizers having higher molecular weights than the conventional oils described above may be used. Polyisobutylene (PIB) is an example of such a plasticizer having a higher molecular weight. For example, medium to high molecular weight PIB may be prepared as OPPANOL TM Brand purchased from BASF TM .

[0033] The amount of plasticizing oil in the gel compound can be any suitable amount, including, but not limited to, about 100 to about 400 parts by weight of the gel compound; about 150 to about 350 parts by weight of the gel compound; and about 200 to about 300 parts by weight of the gel compound.

[0034] Optional additives

[0035] The compounds of the present invention may contain conventional plastic additives in an amount sufficient to provide the compound with the desired processing properties or performance. The amount should not cause waste of additives or be detrimental to the processing or performance of the compound. A person skilled in the art of thermoplastic compounding need not conduct undue experimentation, but only refer to some literature, such as the "Plastics Design Library" (www.williamandrew.com). Plastic Additives Database (Plastics Additives Database) (2004)", many different types of additives can be selected and added to the compound of the present invention.

[0036] Non-limiting examples of optional additives include: adhesion promoters; biocides (antibacterial, fungicides and mildewcides), antifogging agents; antistatic agents; adhesive, foaming and blowing agents, dispersants; fillers and extenders; smoke suppressants; impact modifiers; initiators; lubricants; mica; pigments, colorants and dyes; plasticizers; processing aids; other polymers; mold release agents; silanes, titanates and zirconates; slip and antiblock agents; stabilizers; stearates; UV absorbers; viscosity modifiers; waxes; and combinations thereof.

[0037] The preferred antioxidant is Irganox brand pentaerythritol antioxidant, identified as CAS 6683-19-8. The preferred processing stabilizer is Irgafos brand triaryl phosphite processing stabilizer, identified as CAS number 31570-04-4.

[0038] Range of ingredients

[0039] Table 1 shows acceptable, desirable and preferred ingredient ranges for the gel compounds of the present invention.

[0040]

[0041] Remolding into plastic products

[0042] For pellets of thermoplastic elastomer compound made by continuous extrusion processing, one of ordinary skill in the art can reshape the pellets into any conceivable plastic article having a Shore OO hardness of less than about 60 without undue experimentation.

[0043] Subsequent extrusion or molding techniques are well known to those skilled in the art of thermoplastic polymer engineering. Without undue experimentation, and only by referring to references such as "Extrusion, The Definitive Processing Guide and Handbook"; "Handbook of Molded Part Shrinkage and Warpage"; "Specialized Molding Techniques"; "Rotational Molding Technology" and "Handbook of Mold, Tool and Die Repair Welding" (all published by Plastics Design Library (www.williamandrew.com)), one skilled in the art can use the compounds of the present invention to make articles of any desired shape and appearance.

[0044] Typical processes for molding such soft thermoplastic elastomer compounds include casting, rotational molding, slush molding, extrusion coating, injection molding, compression molding, transfer molding, and dip molding. Such soft thermoplastic elastomer compounds can also be overmolded or extruded onto rigid substrates. Such soft thermoplastic elastomer compounds can also be melted in a melt tank and pumped into the mold as a liquid.

[0045] The low hardness thermoplastic elastomer compounds of the present invention can exhibit low melt viscosity values. Alternatively, the compounds of the present invention can be processed by a pourable or dispensed gel process.

[0046] Practicality of the Invention

[0047] The gel compound of the present invention has excellent versatility as a molded gel plastic article due to the presence of a large amount of plasticizer oil, wherein the plasticizer oil does not bleed out when used at temperatures between about 40°F and 110°F.

[0048] The antioxidant properties and thermal stability added by these respective functional additives give the gel compound the durable properties that any gel-like plastic article should have.

[0049] The resulting thermoplastic elastomer can be used for injection molding of plastic articles that benefit from the highly elastic molded soft gel compound of the present invention.

[0050] Markets or industries where highly elastic molded soft gel compounds may be introduced include health care (beds, cushions, pillows and bandages); consumer products (comfortable handles for power hand tools, rakes, shovels, lawn mowers, shoes, boots, golf clubs, fishing rods and boats); personal care products (comfortable handles for toothbrushes, razors, combs and hairbrushes); transportation (comfortable grips for steering wheels); and personal apparel (clothing and shoes). Among these many possibilities, the gel compounds are particularly suitable for bedding, pads in wheelchairs and other healthcare pad applications, insoles, toe separators, novelties and toys, pads not related to healthcare, and all types of ergonomic pads.

[0051] Example

[0052] The Examples provide data for evaluating the unpredictability of the present invention.

[0053] Table 2 shows the ingredient list of Examples and Comparative Examples. Table 3 shows the formulations of Examples, Table 4 shows the methods of preparing Examples, and Table 5 shows the physical properties of Examples.

[0054]

[0055]

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[0057]

[0058] Table 6 shows the formulations of other examples, Table 7 shows the methods for preparing other examples, and Table 8 shows the physical properties of other examples.

[0059]

[0060]

[0061]

[0062] Table 9 shows the formulations of other examples, Table 10 shows the methods for preparing other examples, and Table 11 shows the physical properties of other examples.

[0063]

[0064]

[0065]

[0066] The test results show that using only high styrene content SEEPS polymer or only conventional SEEPS polymer does not result in a gel compound having the physical properties required by the present technology. In contrast, a compound containing a combination of high styrene content SEEP copolymer and conventional SEEP copolymer produces a thermoplastic elastomer with good physical properties.

[0067] In one embodiment, combining a high styrene content SEEPS copolymer with a medium molecular weight conventional SEEPS copolymer can provide the most ideal results. In one embodiment, when the ratio of the high styrene content SEEP copolymer to the conventional SEEP copolymer amount is higher, the resulting thermoplastic elastomer has good physical properties. In one embodiment, this can be any suitable ratio, including but not limited to 90:10 high styrene content SEEPS copolymer: conventional SEEPS copolymer; 80:20 high styrene content SEEPS copolymer: conventional SEEPS copolymer; 70:30 high styrene content SEEPS copolymer: conventional SEEPS copolymer; 60:40 high styrene content SEEPS copolymer: conventional SEEPS copolymer; or even 50:50 high styrene content SEEPS copolymer: conventional SEEPS copolymer. When the ratio changes, the physical properties of the gel, such as viscosity, compression set, and hardness may not change in a corresponding similar linear manner.

[0068] Without conventional SEEPS copolymers, high styrene content SEEPS copolymers cannot provide the desired physical properties because the high styrene content SEEPS copolymers themselves quickly rearrange (setup) in the melt, even if their capillary viscosity is not high. Therefore, the combination of copolymers provides the unexpected result of a gel compound with desired physical properties (including but not limited to good viscosity, compression set and hardness). In addition, the gel compound can be formed by conventional injection molding processes.

[0069] Although the above description contains many details, these details should not be construed as limitations on the scope of the invention, but merely as exemplifications of preferred embodiments thereof. Those skilled in the art can envision many other possible variations within the scope and spirit of the invention as defined by the appended claims.

Claims

1. A thermoplastic elastomer gel compound comprising: (a) 40-90 parts by weight of a styrene-ethylene-ethylene-propylene-styrene copolymer having a high styrene content; (b) 10-60 parts by weight of a styrene-ethylene-ethylene-propylene-styrene copolymer having a conventional styrene content; and (c) 200-300 parts by weight of a plasticizer; in, The high styrene content styrene-ethylene-ethylene-propylene-styrene copolymer has a styrene content of greater than 35%, based on the weight of the high styrene content styrene-ethylene-ethylene-propylene-styrene copolymer, and the regular styrene content styrene-ethylene-ethylene-propylene-styrene copolymer has a styrene content of less than 35%, based on the weight of the regular styrene content styrene-ethylene-ethylene-propylene-styrene copolymer; wherein the compound has a Shore OO hardness of 35-52; wherein the ratio of the high styrene content styrene-ethylene-ethylene-propylene-styrene copolymer to the normal styrene content styrene-ethylene-ethylene-propylene-styrene copolymer is selected from the group consisting of 90:10, 70:30 and 60:40; The styrene-ethylene-ethylene-propylene-styrene copolymer with normal styrene content is selected from the group consisting of styrene-ethylene-ethylene-propylene-styrene copolymer with normal styrene content having a weight average molecular weight of 150,000-250,000 and styrene-ethylene-ethylene-propylene-styrene copolymer with normal styrene content having a weight average molecular weight of 250,000-350,000, or a combination thereof.

2. The compound of claim 1, wherein the high styrene content styrene-ethylene-ethylene-propylene-styrene copolymer is Septon TM J3341.

3. The compound of claim 1 or 2, wherein the styrene-ethylene-ethylene-propylene-styrene copolymer of normal styrene content is selected from the group consisting of Septon TM 4044、Septon TM 4055 or a combination thereof.

4. The compound of claim 1 or 2, wherein the plasticizer is mineral oil.

5. The compound of claim 1 or 2, wherein the compound has a compression set of 7-13%.

6. The compound of claim 1 or 2, further comprising adhesion promoters; biocides; antifogging agents; antistatic agents; adhesives, foaming agents and blowing agents; dispersants; fillers and extenders; flame retardants and smoke suppressants; impact modifiers; initiators; lubricants; pigments and dyes; mold release agents; slip and antiblock agents; stabilizers; ultraviolet light absorbers; viscosity modifiers; and combinations thereof.

7. The compound of claim 1 or 2, further comprising mica; colorants; stearates; waxes; silanes, titanates and zirconates, and combinations thereof.

8. A thermoplastic article comprising the compound of any one of claims 1 to 7.

9. The article of claim 8, wherein the article has a Shore OO hardness of 35 to 52.

10. The article of claim 8 or 9, wherein the article is injection molded.

11. A method of molding a compound as claimed in any one of claims 1 to 7, the method comprising the steps of: (a) placing the compound into a drum dispensing unit; (b) heating the compound in an integral melter; (c) heating the compound along the dispensing hose; (d) heating the compound at a dispensing nozzle; and (e) dispensing the compound into a mold.

12. The method of claim 11, wherein the heating of steps (b), (c) and (d) occurs at a temperature in the range of 120°C to 240°C.

13. The method of claim 11 or 12, wherein the mold is an open mold cavity.

14. A method as claimed in claim 11 or 12, wherein the mould is a closed mould cavity with sufficient ventilation to allow air displacement.

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