Gel elastomer formulation

Abstract

Provided is a gel elastomer composition including a homogenous blend of a styrene-based thermoplastic elastomer and a plasticizer, combined in an elastomer-plasticizer ratio, the composition further including a thermoplastic resin selected from the group consisting of a low-density elastomer and a high-molecular weight plastic, added to the composition so as to maintain the elastomer-plasticizer ratio. The low density elastomer is preferably a polyolefin thermoplastic elastomer or an ethylene-vinyl acetate copolymer. The high molecular weight plastic is preferably a high molecular weight polyethylene or a ultra-high molecular weight polyethylene. The elastomer-plasticizer ratio is preferably 100-150 parts elastomer to 450-600 parts plasticizer. The added thermoplastic resin is preferably 10-40 parts, more particularly 10-25 parts.

Description

GEL ELASTOMER FORMULATION Technical Field

[0001] Embodiments of the disclosure relate generally to gel cushioning materials.  Specific embodiments relate to particular combinations and compositions of components to form elastomeric cushioning materials with desirable properties.Background Art

[0002] Thermoplastic elastomer materials can be made into soft and elastic gel elastomer materials by adding plasticizers, and such gel elastomer materials can be made into multi-wall grid structures by thermoplastic forming, to be used as a comfortable cushion to relieve pressure.  However, traditional gel elastomer materials have notable defects, such as the gel elastic material feeling sticky to the touch resulting in a poor consumer experience. In addition, when the traditional gel elastomer material is squeezed and contacted for a long time, the multi-walled grid structure will often stick together.  The traditional solution is to spray an ultrafine polymer powder on the surface, but the ultrafine polymer powder will fall off during long-term use, enter the air, and can be inhaled by users, affecting health.

[0003] This patent provides an improved composition.  By optimizing the formula system, the sticky feel on the surface of the gel elastomer materials can be significantly reduced. At the same time, the improved formula has an improved mechanical response curve, which can effectively reduce the adhesion of the grid structure.

[0004] Other drawbacks of traditional gel elastomer materials include degradation and excessive adhesion, especially when used in cushion applications. The high tackiness of these materials causes them to stick to themselves, making it difficult to reposition or reshape the cushion. This adhesion will cause adjacent surfaces in the grid structure to adhere to each other, causing the stable support structure to change. Such changes would reduce the supporting ability of the cushion and hinder the ability to adjust the shape of the cushion and orient according to individual preferences, resulting in discomfort for users who prefer a more customized sleeping experience.

[0005] Another shortcoming of traditional elastomer technology is the sticky textural feel. These materials tend to have a gummy surface that can attract dirt, dust, and other particles, leading to contamination issues. The stickiness can also impede smooth handling and assembly processes, affecting overall efficiency in industrial settings. Additionally, the tackiness of gel elastomers can result in difficulties in removing products or components from manufacturing molds, leading to production delays and increased labor requirements.

[0006] The sticking tendency of gel thermoplastic elastomer materials can also lead to issues related to hygiene and cleanliness. The adhesion between different parts of the pillow can create pockets or crevices where dirt, dust, sweat, and skin particles can accumulate over time. This can potentially lead to the growth of bacteria or allergens, compromising overall hygiene and potentially causing allergic reactions or respiratory problems for users. The difficulty in cleaning and maintaining such pillows further exacerbates this issue.

[0007] Durability is another area where traditional gel elastomers fall short, the excessive adhesion of gel thermoplastic elastomer materials can impact the longevity and durability of pillows. The sticking together of different layers or sections of the pillow can result in premature wear and tear, as the constant pulling or stretching required to separate the adhered parts can lead to material degradation. This can ultimately reduce the pillow's lifespan and necessitate more frequent replacements, adding to the overall cost and inconvenience for users.

[0008] Traditional solutions include spraying ultra-fine polymer powder on the surface, but the ultra-fine polymer powder may come off during long-term use, enter the air, and be inhaled by people, which may affect health. Such methods are unsuitable and present heath concerns for consumers.

[0009] The realm of polyolefins offers an incredible scope for innovation and development, as the number of possible polyolefins manufacturers can create is enormous. Polyolefins are derived from simple monomers, such as ethylene and propylene, and can be modified in numerous ways to yield a vast array of unique properties. By adjusting the polymerization conditions, catalysts, and additives, the possibilities for creating new polyolefins are virtually limitless.

[0010] The sheer number of polyolefin variations stems from the immense versatility of their molecular structure. The polymer chains can be manipulated to exhibit a wide range of molecular weights, branching structures, and degrees of crystallinity. These variations, combined with the ability to incorporate additives and modifiers, allow for an extensive palette of material properties. From flexible and transparent films to rigid and impact-resistant components, polyolefins can be fine-tuned to fulfill diverse needs in packaging, automotive, construction, and countless other sectors including household consumer goods.

[0011] Manufacturers, especially for household consumer products, choose not to use low density elastomer when making thermoplastic elastomer (TPE) pillows for several reasons. Firstly, low density elastomers typically have lower durability and resilience compared to higher density counterparts. Pillows require a certain level of firmness and support to provide optimal comfort and maintain their shape over time. Low density elastomers may not possess the necessary structural integrity to withstand prolonged use and may lose their shape and effectiveness more quickly. This could result in a shorter lifespan for the pillows, leading to customer dissatisfaction and increased warranty claims, which can be costly for manufacturers.

[0012] Secondly, low density elastomers often have lower tear and abrasion resistance. Pillows are subjected to various stresses and strains, such as body weight, movement, and friction. If the elastomer used in the TPE pillow has low tear and abrasion resistance, it may lead to premature wear and tear, reducing the pillow's overall quality and comfort. Manufacturers strive to provide pillows that can withstand everyday use without significant damage or deterioration. By opting for higher density elastomers with better tear and abrasion resistance, they can ensure the pillows maintain their integrity and offer long-lasting performance, enhancing customer satisfaction and brand reputation.

[0013] Ethylene octene polyolefin (EO) is a low-density elastomer that has gained popularity as a thermoplastic elastomer (TPE) in some industrial application. However, it presents drawbacks when used in manufacturing pillows. Firstly, EO-based TPEs tend to have a relatively high density, which can make pillows constructed from this material feel heavier and bulkier compared to other options. This additional weight can reduce the overall comfort and ease of handling, affecting the user's sleeping experience and maneuverability of the pillow.

[0014] Another drawback of using EO polyolefin in pillow manufacturing is its limited softness and cushioning properties. EO-based TPEs often have a relatively higher durometer hardness, resulting in a firmer feel. While this may be desirable in certain applications, it can be less suitable for pillows, which require a balance between support and comfort. The lack of adequate softness and cushioning can lead to reduced pressure relief and inadequate neck and head support, potentially resulting in discomfort or disrupted sleep for users.

[0015] Furthermore, EO polyolefin TPEs may exhibit limited breathability, which can negatively impact the pillow's performance. These materials can hinder airflow and ventilation, potentially leading to heat retention and moisture buildup during sleep. This lack of breathability can make pillows constructed with EO-based TPEs feel warmer and less conducive to a cool and comfortable sleeping environment. Improper temperature regulation can cause night sweats, discomfort, and disrupted sleep patterns for users. Considering these drawbacks, manufacturers in the pillow industry are likely to explore alternative TPE materials to avoid the limitations of density, softness, and breathability.

[0016] A need exists to explore innovative approaches to polyolefin elastomer production, such as metallocene catalysts and controlled polymerization techniques, to unlock new possibilities in polyolefin synthesis.

[0017] Ethylene-vinyl acetate copolymer (EVA) is a low-density elastomer that also presents problems for use in TPE pillow manufacturing. EVA-based TPEs have a relatively low melting point, which can make them susceptible to deformation and loss of shape under elevated temperatures. Pillows are subject to body heat and pressure during use, and if the EVA-based TPE lacks adequate heat resistance, it may lose its structural integrity, leading to sagging or flattening of the pillow over time. This can result in reduced support and comfort, diminishing the overall sleeping experience.

[0018] Another drawback of using EVA-based TPEs in pillow manufacturing is their tendency to exhibit a relatively higher compression set. Compression set refers to the ability of a material to recover its original shape after being compressed. EVA-based TPEs may have limited resilience, and once compressed by the weight of the head or body, they may not fully bounce back or reform, causing permanent deformation or indentation. This can lead to uneven support and a loss of the pillow's intended shape, ultimately impacting comfort and sleep quality.

[0019] Furthermore, EVA-based TPEs can have a higher gas permeability compared to other materials. This means that pillows made from EVA-based TPEs may be more prone to air and moisture permeation, resulting in reduced durability and potential issues with odor absorption or retention. The increased gas permeability can also affect the pillow's ability to maintain its loft and shape over time, as the escape of trapped air can lead to deflation or flattening. This drawback may compromise the longevity and performance of pillows made from EVA-based TPEs.

[0020] Manufacturers in the pillow industry continue to seek TPE materials with higher heat resistance, better compression set properties, and improved adhesion resistance. The inventive gel elastomer formulations address these limitations and ensure that pillows retain their shape, support, and durability throughout extended periods of use.

[0021] For the foregoing reasons, gel thermoplastic elastomer material manufacturers, especially in the pillow industry continue attempting to develop formulations that minimize long felt drawbacks including adhesion without compromising the material's desired properties, such as comfort and support. Improvements in material design, surface treatments, or the introduction of anti-adhesion coatings can help mitigate the sticking issues and enhance the overall user experience when using gel thermoplastic elastomer pillows.Technical Solution

[0022] The present invention is directed to a gel elastomer composition of a homogenous blend of a styrene-based thermoplastic elastomer and a plasticizer, combined in an elastomer-plasticizer ratio.  The inventive composition further includes a thermoplastic resin that may be selected from the group consisting of a low-density elastomer or a high-molecular weight plastic, such thermoplastic resin added to the composition so as to maintain the elastomer-plasticizer ratio.  The plasticizer is oil-based, preferably selected from the group consisting of mineral oil or vegetable oil.  The plasticizer preferably has a viscosity of between 5 mm2 / s and 100 mm2 / s at 40 degrees Celsius.

[0023] The styrene-based thermoplastic elastomer may be selected from the group consisting of styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-hexene butene- styrene copolymers, and styrene-ethylene propylene -styrene copolymers.  The low-density elastomer may be selected from the group consisting of polyolefin thermoplastic elastomer and ethylene-vinyl acetate copolymer, and the high-molecular weight plastic may be selected from the group consisting of high molecular weight polyethylene and ultra-high molecular weight polyethylene.

[0024] The inventive composition may further include a stabilizing agent, a release agent, a deodorizer, or a colorant.  The stabilizing agent may be selected from the group consisting of hindered phenolic antioxidants, phosphite antioxidants, metal passivators, ultraviolet absorbers, radical scavengers, and hydrogen peroxide decomposers.  The stabilizing agent may include a first antioxidant and a second antioxidant.  The first antioxidant may be a high molecular weight hindered phenolic antioxidant and the second antioxidant may be a phosphite ester antioxidant.  The release agent may be selected from the group consisting of erucamide, stearic acid amide, oleic acid amide, stearic acid salts, and polyethylene wax.

[0025] The inventive composition may include at least one functional additive consisting of an antimicrobial agent, a fragrance, or a far-infrared ceramic powder.  The elastomer-plasticizer ratio is preferably between 100-150 parts elastomer to 450-600 parts plasticizer.

[0026] In addition to several other additives, which do not relate directly to the benefits of the invention, the inventive gel elastomer has certain required components.  A preferred gel elastomer composition includes 100-150 parts styrene-based thermoplastic elastomer, 450-600 parts plasticizer, and 10-40 parts thermoplastic resin additive.  In a more particularly preferred embodiment, the composition 100-120 parts styrene-based thermoplastic elastomer, 450-550 parts plasticizer, and 10-25 parts thermoplastic resin additive.  The plasticizer is preferably an oil-based compound, such as mineral oil or vegetable oil – specifically a white mineral oil is preferred.  The thermoplastic resin additive is preferably a low-density elastomer (such as POE or EVA) or a high-molecular weight plastic (such as HMWPE or UHMWPE).

[0027] A specific formulation of the preferred gel elastomer composition may include the following: 100 parts styrene-based thermoplastic elastomer, 500 parts white mineral oil plasticizer, and 24 parts low density elastomer EVA.  As described elsewhere, the EVA preferably has a vinyl acetate content of less than 20% by molecular weight, and more preferably less than 12% by molecular weight.  Another specific formulation of the preferred gel elastomer composition may include the following: 100 parts styrene-based thermoplastic elastomer, 500 parts white mineral oil plasticizer, and 20 parts low density elastomer POE.  A third specific formulation of the preferred gel elastomer composition may include the following: 100 parts styrene-based thermoplastic elastomer, 500 parts white mineral oil plasticizer, and 20 parts ultra-high molecular weight plastic UHMWPE.

[0028] Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.Description of Drawings

[0029] These and other features and advantages of the present invention will become appreciated, as the same becomes better understood with reference to the specification, claims and drawings herein:

[0030] FIGURE 1 shows a perspective view of a square grid-style cushion made from elastomer material as described.

[0031] FIGURE 2 shows a partial-cutaway perspective view of the square grid-style cushion of FIG. 1.

[0032] FIGURE 3 shows a perspective view of a triangular-style grid cushion made from elastomer material as described.

[0033] FIGURE 4 shows a perspective view of an alternate embodiment of a triangular-style grid cushion made from elastomer material as described.Mode for Invention

[0034] The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0035] It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present there between. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0036] It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section.

[0037] As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise.  It will be further understood that the terms “comprises” and / or “comprising,” “includes” and / or “including,” and “have” and / or “having,” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0038] Furthermore, relative terms, such as “lower” or “bottom,” and “upper” or “top,” and “inner” or “outer,” may be used herein to describe one element’s relationship to another elements as illustrated in the Figures.  It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.

[0039] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0040] Exemplary embodiments of the present invention are described herein with reference to idealized embodiments of the present invention.  As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected.  Thus, embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. FIGS. 1-4 illustrate examples of cushions manufactured from elastomer materials as described and claimed herein.

[0041] Elastic material compositions can be processed into a multi-wall grid-like structure, and this structure can be manufactured into mattresses, pillows, cushions, and other comfort surfaces that are in contact with the human body. Thermoplastic materials compositions of the type described herein are suitable for making this multi-wall mesh structure and are generally referred to in the industry as gel elastomers. Such known compositions may also include additional stabilizers, release agents, deodorants, toners, and similar additives to the styrene thermoplastic elastomer to form a complete gel elastomer formula system.

[0042] Gel elastomer compositions are achieved by adding oil-based plasticizers to styrenic thermoplastic materials.  The following description improves on existing gel elastomer technology by adding an additional type of polymeric compound designed to improve the characteristics of prior art gel elastomers and address some of the drawbacks described above.

[0043] The novel gel elastomer composition significantly reduces the sticky texture on the surface of the gel elastomer material, and improves the integrity of the resultant gel. As a result, the likelihood of adhesion between walls of the grid structures is reduced. In its most basic form, the composition primarily incorporates a (1) styrene-based thermosplastic, (2) a plasticizer, and (3) a plastic resin additive.

[0044] (1) The styrene-based thermoplastic may include styrene / butadiene / styrene (SBS) block copolymer; styrene / isoprene / styrene (SIS) block copolymer; styrene / hexene-butene / styrene (SEBS) block copolymers and styrene / ethylene-propylene / styrene (SEPS) block copolymers, to name a few examples.  When combined as described herein, the styrene-based thermoplastic can be made into a soft and elastic gel elastomer.

[0045] (2) The plasticizer is an oil-based material such as mineral oil or vegetable oil.  The styrene-based thermoplastic and plasticizer are preferably combined in a preferred ratio of thermoplastic to plasticizer – 100-150 parts elastomer to 450-600 parts plasticizer – discussed more fully below.

[0046] (3) The plastic resin may include low-density elastomers or high-molecular weight engineering plastics. The low-density elastomers are preferably polyolefin (POE) or ethylene-vinyl acetate (EVA), having a density of less than 0.93 g / cm3.  The high-molecular weight engineering plastics are preferably a form of polyethylene (PE) having a number average molecular weight greater than 500,000. In a particular embodiment, the high-molecular weight engineering plastic is preferably ultra-high-molecular-weight polyethylene (UHMW or UHMWPE).  The plastic resin is added to produce an improved elastomer product for manufacturing and is added to the composition in quantities that maintains the composition within the preferred ratio of thermoplastic elastomer to plasticizer.

[0047] The processing technology of the gel elastomer material is to mix various ingredients in the composition in proportion to form a uniform premix, put the premix into an injection molding machine, heat it to 180-280°C to achieve a plastic state, and push the melted gel elastomer composition into the mold.  Once the melted gel elastic is sufficiently cooled the formed gel elastomer is removed from the mold. Through the above process, the gel elastomer premix is processed into a multi-wall grid structure product with a specific shape, preferably a cushion or pillow.

[0048] Styrene-based thermoplastic elastomer is a tri-block polymer. At room temperature, it is characterized by the presence of soft and hard segments in the interpenetrating matrix in a single polymer chain. The poly-styrene end blocks gather together to become hard end blocks with the soft middle blocks forming a pliable structure. For example, in a styrene / butadiene / styrene (SBS) chain, the soft block is the rubbery butadiene central segment, and the hard block is the crystalline styrene end segments. The soft middle blocks are separated from each other by the plasticizers such that the same undergo relative sliding.  At normal temperature, the hard block maintains the elastic material with a stable shape. At higher temperatures, triblock polymers will become fluid and flow under pressure.  When the formed gel elastomer cushion is subjected to a force, relative slippage occurs between the middle blocks, but the end blocks are relatively immobile in a crystalline state, so that after the force is removed, the gel elastomer recovers to the initial undeformed state, thereby generating elasticity.

[0049] Styrenic thermoplastic elastomers can be of the following structures: styrene / butadiene / styrene (SBS) block copolymer; styrene / isoprene / styrene (SIS) block copolymer; styrene / hexene-butene / styrene (SEBS) block copolymers and styrene / ethylene-propylene / styrene (SEPS) block copolymers, to name a few examples.  More preferred are hydrogenated styrene thermoplastic elastomers, especially SEBS, SEPS, SEEPS, etc. Manufacturers of such materials include KRATON, Kuraray, TSRC, etc. The preferred number average molecular weight for such styrenic thermoplastic elastomers is 100,000-300,000, and the preferred common option is a linear structure.

[0050] The gel elastomer material can be thermoformed into a multi-walled grid structure, suitable for use as a comfortable cushioning layer in pillow cushions to relieve user pressure. The composition is further enhanced by adding stabilizing agents, release agents, deodorizers, colorants, etc. to form a complete gel elastomer formulation system.

[0051] The plasticizer material is preferably oil-based, such as mineral oil or vegetable oil. The plasticizer is mixed in the formula and is compatible with the middle block of the styrene-based thermoplastic.  This improves the slippage in the soft middle blocks as described above. Mineral oil is preferably used, generally hydrogenated white mineral oil with a kinematic viscosity of 5-100mm2 / s at 40°C.

[0052] The stabilizing agents are anti-oxidant additives that protect organic substrates against thermo-oxidative degradation so as to ensure the long-term stability of the formula system and are not affected by light, oxygen and other factors that will cause the material to age.  In a preferred embodiment, the stabilizing agent is a combination of hindered phenolic antioxidants and phosphite antioxidants commonly used in the market, metal deactivators, or similar materials. At the same time, light stabilizers, such as ultraviolet absorbers, free radical scavengers or hydroperoxide decomposers, can be included. Stabilizing agents are preferably hindered phenolic antioxidants and phosphite antioxidants such as those produced by BASF under tradenames such as Irganox® 1010 (a sterically hindered primary phenolic antioxidant stabilizer), Irganox® 1076 (a sterically hindered primary phenolic antioxidant stabilizer); Irganox® PS802 (a dialkyl ester of thiodipropionic acid), and Irgafos 168 (a hydrolytically stable phosphite processing stabilizer).

[0053] The processing techniques for gel elastomer materials involves methods known within the art including mixing the various components of the formulation into a homogeneous “premix”, adding the premix to an injection molding machine, heating the injection molding machine to 180-280°C to achieve a plasticized state, pushing the molten gel elastomer into the mold, and waiting for the gel elastomer in the mold to cool before removing it. Through this molding process, the gel elastomer premix is processed into multi-cellular grid structures that can be molded into any desired shape.

[0054] In the actual processing of the prepared compound, since the melted gel elastomer is in direct contact with the metal mold, when the release agent precipitates on the surface of the elastomer, it is guided by the polarity of the metal mold such that the magnetically same end of the dipole is precipitated on the surface of the product. The similar dipoles will produce repulsive intermolecular forces on the surface, thus transforming the sticky feel of the product into a smooth feel.

[0055] Release agents facilitate the removal of formed products from molds. As an additive in the formulation system, during the cooling process, the release agent migrates to the surface of the gel elastomer, forming a slippery surface that reduces the peeling force when the product is removed from the mold. Commonly used release agents include erucamide, stearic acid amide, oleic acid amide, stearic acid salts, or polyethylene wax.  The addition of release agents can be done as needed or omitted if desired.

[0056] Deodorizers can also be added to absorb or eliminate odor molecules in the polymer system. Colorants can be added to adjust the color of the polymer. Optionally, functional additives such as antimicrobial agents, fragrances, far-infrared ceramic powder, etc., can also be added to the formulation system to prepare functional gel elastomer materials.

[0057] The precipitation of release agents on the surface of the gel elastomer can form a precipitate layer, creating a smooth touch and preventing the walls of the grid from adhering together. However, even with the presence of release agents, adhesion may still occur under large compression forces. These forces can be generated during normal use, such as compression during volume reduction, the weight of the elastomer itself, or the weight of the human body. When two adjacent walls of the grid are forcefully compressed, the material undergoes significant local stretching due to high elongation, and the anti-adhesion medium is insufficient to cover the surface of the stretched material. The interaction between the middle blocks in the styrene thermoplastic elastomer and the unsaturated hydrocarbons in the plasticizer occurs, and the irregular distribution of the middle blocks and the plasticizer's unsaturated hydrocarbons results in direct molecular attraction between molecules with different dipole moments. Over time, this can lead to the formation of strong intermolecular forces and local adhesion. Therefore, reducing the elongation of the material can effectively reduce this adhesion phenomenon.

[0058] The addition of a plastic resin additive sets the claimed composition apart from the prior art, particularly in the form and ratios of either the low-density elastomer and / or the high-molecular weight plastic.  The selection of improved plastic resin additive materials added to the formulation system enhances the completed gel elastomer product.  By crystallization and combination with the thermoplastic elastomer grid, the elongation at break of the product is reduced. The specific mechanism is as follows.

[0059] The polystyrene segment (S segment) in the molecular chain of the thermoplastic elastomer contains benzene rings, which are rigid and have poor mobility. The mid-block segment of the molecular chain is a straight chain carbon with side chains, which has high flexibility. The difference in flexibility between the two segments results in a “hard segment dispersed phase” distributed in a "soft segment continuous phase" to form a physical cross-linked network, which hinders the free movement of the soft segment and imparts good resilience to the finished product, particularly making SEBS perform with greater resiliency.

[0060] The plastic resin additive, particularly a low-density elastomer is a semi-crystalline resin, which undergoes a crystallization process at high temperatures. The crystallization process of the low-density elastic material includes two stages: nucleation and crystal growth. In the nucleation stage, the polymer chain segments are arranged in a regular manner to form a large enough thermodynamically stable nucleus, and then the nucleus grows to form spherulites, entering the stage of crystal growth, until the crystallization is completed to form a stable crystalline structure.

[0061] Even a small amount of plastic resin (low density elastomer or high molecular weight engineering plastic) added to the thermoplastic elastomer material for blending provides benefits. After high-temperature melting, the glassy microdomains (mid-block segments) in the thermoplastic elastomer and the crystalline microdomains of the plastic resin can form a thermoplastic interpenetrating polymer network (TIPN). The formation of crystals reduces the flexibility of the mid-block segments, requiring a higher force for their free movement, which macroscopically manifests as a need for greater elongation to break the material, enhancing the tensile strength of the gel elastomer material.

[0062] The preferred low-density elastomer material is POE or EVA having a density of less than 0.93 g / cm3. The preferred high-molecular weight engineering plastics are forms of ultra-high molecular weight PE (UHWMPE or HMPE), having a number average molecular weight greater than 500,000.

[0063] In practical use, while keeping the ratio of thermoplastic elastomer and plasticizer unchanged, it is also desired to maintain the hardness of the thermoplastic elastomer material unchanged. Adding as much plastic resin material as possible is conducive to improving the overall crystallinity of the material and thereby enhancing the tensile strength of the gel elastomer material. Preferably the styrene-based thermoplastic maintains at least 70% of the total thermoplastics in comparison to the plastic resin added.

[0064] POE thermoplastic elastomer is produced by in-situ polymerization of ethylene and octene using metallocene catalysts.  The compound exhibits the soft chain coil structure of octene chains and the crystalline ethylene chains serve as physical cross-linking points, providing excellent toughness and good processability. POE (Polyolefin Elastomer) has no unsaturated double bonds in its molecular structure and exhibits excellent aging resistance. POE has a narrow molecular weight distribution, and good compatibility with polyolefins. Good flowability can improve the dispersion of fillers, and also enhance the melt fusion strength of products.

[0065] It is crucial to maintain the overall density of the gel elastomer product unchanged while maximizing the amount of POE added. Therefore, the density of POE material is a key parameter that affects the hardness of gel elastomer material. It is preferred to use POE with a density of 0.850-0.910 g / cm3.

[0066] EVA is a common polymer having a molecular formula of (C2H4)x(C4H6O2)y. EVA should only be used as a plastic when the vinyl acetate (C4H6O2) content is below 20%. EVA exhibits good low-temperature resistance, with a relatively low thermal decomposition temperature of around 230°C. As the molecular weight increases, the softening point of EVA rises, while processability and surface gloss of molded parts decrease, but strength, impact toughness, and resistance to environmental stress cracking improve. In terms of chemical resistance and oil resistance, EVA is slightly inferior to polyethylene (PE) and polyvinyl chloride (PVC), and this difference becomes more pronounced with increasing vinyl acetate content.

[0067] In the gel elastomer formulation system, reagent crystallinity is an important factor in selection. The lower the amount of branching on the molecular chain, the stronger the crystallization ability of the molecular chain. Therefore, EVA with vinyl acetate content (VA content) of less than 12% is preferred. In addition, considering the impact of hardness on the material, EVA with a density range of 0.850-0.910 g / cm3 is preferred.

[0068] The high molecular weight engineering plastic has a linear structure and excellent comprehensive properties, with a number average molecular weight greater than 500,000 – exhibiting low density, good wear resistance, self-lubrication, impact resistance, corrosion resistance and similar qualities.  UHMWPE itself has good self-lubrication and non-stickiness, and the effect shown in actual tests is better than that of EVA and POE.  In a particularly preferred embodiment, the preferred density range of UHMWPE is 0.92-0.96 g / cm3, and a small amount of UHMWPE in this density range will not have a great impact on the overall softness or hardness of the gel elastomer product. Since UHMWPE has melt flow rate of less than 5g / 10min, it is difficult to disperse and melt in the overall composition system.  To address this dispersion issue, it is preferable to select UHMWPE having a particle size, preferably in a range of 20-500μm, while still having a number average molecular weight greater than 500,000.

[0069] Embodiments of the present disclosure are provided in relative ratios of amounts, not specific quantities.

[0070] A first exemplar embodiment of the inventive gel elastomer composition provides for 100 parts of styrene-based thermoplastic elastomer, 500 parts of white mineral oil plasticizer, 12 parts of linear low-density polyethylene, and lesser quantities of other additives, e.g., antioxidants, release agents, colorants, odor eliminators, etc.

[0071] A second exemplar embodiment of the inventive gel elastomer composition provides 100 parts of styrene-based thermoplastic elastomer, 500 parts of white mineral oil plasticizer, 24 parts of EVA (VA content 20%), and lesser quantities of other additives, e.g., antioxidants, release agents, colorants, odor eliminators, etc.

[0072] A third exemplar embodiment of the inventive gel elastomer composition provides 100 parts of styrene-based thermoplastic elastomer, 500 parts of white mineral oil plasticizer, 24 parts of EVA (VA content 12%), and lesser quantities of other additives, e.g., antioxidants, release agents, colorants, odor eliminators, etc.

[0073] A fourth exemplar embodiment of the inventive gel elastomer composition provides 100 parts of styrene-based thermoplastic elastomer, 500 parts of white mineral oil plasticizer, 20 parts of POE, and lesser quantities of other additives, e.g., antioxidants, release agents, colorants, odor eliminators, etc.

[0074] A fifth exemplar embodiment of the inventive gel elastomer composition provides 100 parts of styrene-based thermoplastic elastomer, 500 parts of white mineral oil plasticizer, 20 parts of UHMWPE, and lesser quantities of other additives, e.g., antioxidants, release agents, colorants, odor eliminators, etc.

[0075] A sixth exemplar embodiment of the inventive gel elastomer composition provides 100 parts of styrene-based thermoplastic elastomer, 500 parts of white mineral oil plasticizer, 40 parts of UHMWPE, and lesser quantities of other additives, e.g., antioxidants, release agents, colorants, odor eliminators, etc.

[0076] Embodiments of the present disclosure were subjected to extensive experimentation, performing both peeling testing and tensile strength testing.

[0077] The peeling testing was performed using a BLD-CH electronic peel tester as known in the art. Horizontal peel force testing was analyzed horizontally to a contact surface. The testing sample was cut into strips with two sample strips stacked on top of each other with a weight placed above the stack. Force was applied in opposite directions on the two sample strips to peel them apart, and the maximum force value during the peeling process was measured to reflect the friction between the two samples.  Vertical Peel Force Testing was conducted perpendicular to a contact surface. Two sample strips were stacked and compressed with a force of 200N (Newtons). After compression, the peel force value was measured to reflect the direct adhesive force between the samples.

[0078] Tensile strength testing was performed to determine the force value required to achieve 300% elongation from a non-stressed state.

[0079] The results of the testing on the above reported embodiments were as below:

[0080] Analysis guiding development of the embodiments is as follows. The smaller the peeling force value – both horizontal and vertical – the easier the sample material is to separate. The smaller the vertical peeling test force value the stronger the anti-extrusion adhesion ability.  The greater the tensile force value of the material, the stronger the corresponding tensile strength.  After release agent precipitates, the surface becomes smooth, resulting in lower horizontal peel test force data.

[0081] In embodiment 1, adhesion occurred after vertical extrusion, resulting in poor vertical peel test data. In embodiment 2, attempts were made to improve the extrusion adhesion phenomenon based on Example 1, but there was not much improvement due to the selection of EVA having greater than 20% VA content. In embodiments 3 and 4, more preferable material parameters were chosen, effectively improving the resistance to extrusion adhesion compared to Example 2, as well as improved tensile strength. In Examples 5 and 6, the resin additive was changed to UHWMPE, further improving both the resistance to extrusion adhesion and tensile strength.

[0082] Based on the foregoing examples and experimental evaluation, the preferred ratios of primary components in the inventive gel elastomer composition fall into the following relative ranges: for every 100-150 parts of thermoplastic elastomer, there is provided about 450-600 parts of plasticizer and about 10-40 parts plastic resin (low density or high-molecular weight).  In addition, the composition may include lesser quantities of other additives, e.g., antioxidants, release agents, colorants, odor eliminators, etc. – all without altering characteristics of the gel elastomer composition and preferred ratio of thermoplastics to plasticizer described above.

[0083] Although several embodiments have been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention.

Claims

1.A gel elastomer composition comprising a homogenous blend of a styrene-based thermoplastic elastomer and a plasticizer, combined in an elastomer-plasticizer ratio, the composition further comprising:a thermoplastic resin selected from the group consisting of a low-density elastomer and a high-molecular weight plastic, added to the composition so as to maintain the elastomer-plasticizer ratio.2.The gel elastomer composition of claim 1, wherein the plasticizer is oil-based and selected from the group consisting of mineral oil and vegetable oil.3.The gel elastomer composition of claim 1, wherein the plasticizer has a viscosity of between 5 mm2 / s and 100 mm2 / s at 40 degrees Celsius.4.The gel elastomer composition of claim 1, wherein the styrene-based thermoplastic elastomer is selected from the group consisting of styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-hexene butene- styrene copolymers, and styrene-ethylene propylene -styrene copolymers.5.The gel elastomer composition of claim 1, wherein said low-density elastomer is selected from the group consisting of polyolefin thermoplastic elastomer and ethylene-vinyl acetate copolymer, and the high-molecular weight plastic is selected from the group consisting of high molecular weight polyethylene and ultra-high molecular weight polyethylene.6.The gel elastomer composition of claim 1, further comprising a stabilizing agent, a release agent,  a deodorizer, or a colorant.7.The gel elastomer composition of claim 6 wherein said stabilizing agent is selected from the group consisting of hindered phenolic antioxidants, phosphite antioxidants, metal passivators, ultraviolet absorbers, radical scavengers, and hydrogen peroxide decomposers.8.The gel elastomer composition of claim 7, wherein the stabilizing agent comprises a first antioxidant and a second antioxidant. 9.The gel elastomer composition of claim 8, wherein said first antioxidant is a high molecular weight hindered phenolic antioxidant. 10.The gel elastomer composition of claim 9, wherein said second antioxidant is a phosphite ester antioxidant. 11.The gel elastomer composition of claim 6 wherein said release agent is selected from the group consisting of erucamide, stearic acid amide, oleic acid amide, stearic acid salts, and polyethylene wax. 12.The gel elastomer composition of claim 1, further comprising at least one functional additive consisting of an antimicrobial agent, a fragrance, or a far-infrared ceramic powder.13.The gel elastomer composition of claim 1, wherein the elastomer-plasticizer ratio is between 100-150 parts elastomer to 450-600 parts plasticizer.14.The gel elastomer composition of claim 1, wherein the composition comprises:   100-150 parts styrene-based thermoplastic elastomer;    450-600 parts plasticizer; and   10-40 parts thermoplastic resin.15.The gel elastomer composition of claim 14, wherein the composition comprises:    100-120 parts styrene-based thermoplastic elastomer;    450-550 parts plasticizer; and   10-25 parts thermoplastic resin.16.The gel elastomer composition of claim 14, wherein the composition comprises:    100 parts styrene-based thermoplastic elastomer;    500 parts white mineral oil plasticizer; and   24 parts ethylene-vinyl acetate copolymer, having a vinyl acetate content of less than 20% by molecular weight.17.The gel elastomer composition of claim 14, wherein the composition comprises:   100 parts styrene-based thermoplastic elastomer;    500 parts white mineral oil plasticizer; and   20 parts polyolefin thermoplastic elastomer.18.The gel elastomer composition of claim 14, wherein the composition comprises:   100 parts styrene-based thermoplastic elastomer;    500 parts white mineral oil plasticizer; and   20 parts high molecular weight polyethylene.19.The gel elastomer composition of claim 14, wherein the composition comprises:   100 parts styrene-based thermoplastic elastomer;    500 parts white mineral oil plasticizer; and   20 parts ultra-high molecular weight polyethylene.20.A gel elastomer composition comprising a homogenous blend of a styrene-based thermoplastic elastomer and a plasticizer, combined in an elastomer-plasticizer ratio of 100-150 parts elastomer to 450-600 parts plasticizer, the composition further comprising:a thermoplastic resin selected from the group consisting of polyolefin thermoplastic elastomer, ethylene-vinyl acetate copolymer, high molecular weight polyethylene, and ultra-high molecular weight polyethylene, added to the composition so as to maintain the elastomer-plasticizer ratio.

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