JP7222577B2 - shock absorber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a shock absorbing material obtained by curing or molding a resin composition for shock absorption based on a polymer viscoelastic resin, and in particular, a shock absorbing material having excellent shock absorption even with a thickness of 0.5 mm or less. Regarding.

BACKGROUND ART Various electronic devices such as personal computers, mobile phones, and electronic paper are being used on a daily basis while being carried or carried, and are becoming smaller and thinner. In this way, when using various electronic devices while carrying them, there is a possibility that the electronic device will be damaged if the electronic device is dropped during operation or if some unexpected external force is applied. Since mechanical parts are densely mounted in a narrow housing, they are more susceptible to these damage factors. Therefore, various impact absorbing materials are applied as a means of reducing the influence of damage factors and ensuring the durability of products. These shock absorbing materials are required to be thin due to space constraints accompanying the miniaturization of electronic devices. is reduced, the impact absorption performance is lowered. Therefore, the development of impact absorbing materials that achieve both thinness and impact absorption is underway.

Therefore, Patent Document 1 discloses a thin shock-absorbing material having a thickness of 0.5 to 2.0 mm, which is obtained by blending a filler with a silicone gel, and the filler is 1 to 3 parts per 100 parts by weight of the silicone gel. .5 parts by weight of micro hollow bodies having an outer shell of synthetic resin and 10 to 30 parts by weight of silica, and the thin shock-absorbing material has an Asker C hardness of 15 to 60, and the silicone gel has an Asker C hardness of 15 to 60. A thin shock-absorbing material having a value of 5 to 55 has been proposed. This thin shock-absorbing material has a shock-absorbing efficiency of 70% or more in a weight drop test. In addition, by adding silica particles to increase mechanical strength and fatigue durability, we are aiming to achieve both thinness and shock absorption of the impact cushioning material. However, in recent years, there has been a demand for a shock absorbing material with a thickness of 0.5 mm or less, and it is difficult to obtain sufficient shock absorbing properties simply by reducing the thickness of the thin shock absorbing material of Patent Document 1. Met.

Therefore, as a shock absorbing material having a thin thickness of 0.5 mm or less and excellent shock absorbing properties, a shock absorbing sheet shown in Patent Document 2 has been proposed. This impact-absorbing sheet is made of a resin foam having closed cells, and has a thickness of 0.02 to 1.0 mm. The oblateness is 0.5 to 1.9, and by making the closed cells in the resin foam have a specific structure, excellent impact absorption can be obtained even in a thinner area. .

JP 2012-102878 A JP 2014-214205 A

However, the impact-absorbing sheet of Patent Document 2 is a resin foam having closed cells, and the gas filled in the closed cells is a compressible substance. Therefore, when the magnitude of the impact exceeds a certain level, the bubbles tend to collapse in the thickness direction, resulting in a bottomed state, which limits the range in which the impact can be absorbed. This tendency was more pronounced as the hardness of the base resin of the resin foam was decreased in order to increase the impact absorption.

Therefore, the present invention solves the above-mentioned problems of the prior art, and its object is to provide a shock absorbing material that has a large range of shock absorption and excellent shock absorption even with a thin thickness of 0.5 mm or less. That is.

In order to solve the above-mentioned problems, the present inventors studied compositions by combining various components for the base resin component and the filler component, which are the materials of the shock absorbing material, and investigated the impact on the shock absorbing performance at a thin thickness. As a result of research, by blending specific resin particles into the base polymer viscoelastic resin, it is possible to create a thin shock absorber with a thickness of 0.5 mm or less, a shock absorber formed from a single base resin, a polymer Compared to the shock absorbing material described in Patent Document 1 in which a micro hollow body having a synthetic resin outer shell is added to a viscoelastic resin, and the shock absorbing material described in Patent Document 2 made of a resin foam having closed cells, It was found that a shock absorbing material having excellent shock absorbing properties can be obtained. Based on these findings, the present invention has been completed.

In order to solve the above problems, the impact absorbing material of the present invention comprises a cured product or molded product of a resin composition for impact absorption, which is obtained by dispersing fine resin particles (B) in a polymer viscoelastic resin (A). is 0.5 mm or less, and the fine resin particles (B) are solid particles having elasticity with a compressive strength Fc of 0.06 to 10 MPa obtained by the following formula (1),

(In the formula (1), R is the particle size (μm) of the resin fine particles (B), Fm is the compressive strength at 10% compression strain measured in accordance with JIS K6254 D method of the resin fine particles (B) (10% deformation compressive stress).)
The hardness of the cured or molded product of the polymer viscoelastic resin (A) is 100 to 170 in terms of penetration (according to JIS K2207, 25°C), and the cured or molded product of the impact-absorbing resin composition. The hardness is 70 to 170 in terms of penetration (according to JIS K2207, 25°C).

The impact-absorbing resin composition constituting the impact-absorbing material of the present invention has a compressive strength Fc (10% compression measured according to JIS K6254 D method) as resin fine particles (B) in the polymer viscoelastic resin (A). The value obtained by converting the compressive strength Fm under strain as the compressive strength Fc of spherical resin fine particles having a particle size of 10 μm) is dispersed with solid particles having elasticity of 0.06 to 10 MPa, and a resin composition for impact absorption. The hardness of the cured or molded product is 70 to 170 in terms of penetration (25°C) in accordance with JIS K2207, and the hardness of the cured or molded product of the polymer viscoelastic resin (A) is in accordance with JIS K2207. It is 100 to 170 in terms of penetration (25° C.). With this configuration, the dynamic viscoelastic deformation of the polymer viscoelastic resin (A) and the effects of deformation of the fine resin particles (B) and changes in the distance between particles work together to achieve excellent impact absorption. In addition, since the fine resin particles (B) are solid particles having elasticity due to a predetermined compressive strength, the deformation of the polymer viscoelastic resin (A) is moderately suppressed. As a result, it is possible to obtain a shock absorbing material that is less likely to bottom out and has excellent shock absorbing performance in a thin region of 0.5 mm or less, particularly 0.1 mm or more and 0.5 mm or less. In addition, by adopting the above-described configuration, in the thin shock absorbing material having a thickness of 0.5 mm or less, the shock absorbing material formed from the base polymer viscoelastic resin (A) alone, or the polymer viscoelastic resin ( Compared to conventional shock absorbers to which hollow resin particles are added to A) or shock absorbers made of a resin foam having closed cells, a shock absorber that is less likely to bottom out and has excellent shock absorbency can be obtained. .

Further, the blending ratio of the fine resin particles (B), which is blended in the impact-absorbing resin composition of the impact-absorbing material of the present invention, is 5 to 40 parts by weight with respect to 100 parts by weight of the high-molecular-weight viscoelastic resin (A). is also preferred. As a result, the synergistic action of the polymer viscoelastic resin (A) and the fine resin particles (B) is exhibited more effectively, so that the thin region of 0.5 mm or less is less likely to bottom out, A shock absorbing material that can achieve excellent shock absorbing performance is obtained.

It is also preferable that the average particle size of the fine resin particles (B), which is incorporated in the impact-absorbing resin composition of the impact-absorbing material of the present invention, is 0.5 to 50 μm. As a result, the action involving the fine resin particles (B) is exhibited more effectively, so that in a thin area of 0.5 mm or less, it is less likely to bottom out, and excellent impact absorption performance can be achieved. A shock absorbing material is obtained.

It is also preferable that the resin fine particles (B), which are blended in the impact-absorbing resin composition of the impact-absorbing material of the present invention, are spherical. As a result, the synergistic action in which the dynamic viscoelastic deformation of the polymer viscoelastic resin (A) and the actions such as the deformation of the fine resin particles (B) and the change in the inter-particle distance function uniformly and smoothly. Therefore, it is possible to obtain a shock absorbing material that is less likely to bottom out in a thin region of 0.5 mm or less and that can achieve excellent shock absorbing performance.

It is also preferable to provide a coating layer in which the resin fine particles (B), which are blended in the impact-absorbing resin composition of the impact-absorbing material of the present invention, coat the entire surface. As a result, the properties of the coating layer are combined with the fine resin particles (B), so that the effects of the fine resin particles (B) can be diversified, so that in a thin region of 0.5 mm or less, a more bottomed state can be achieved. It is difficult to obtain a shock absorbing material that achieves excellent shock absorbing performance and diversifies its action.

Further, it is also preferable that the resin fine particles (B) blended in the impact absorbing resin composition of the impact absorbing material of the present invention are silicone resin fine particles or acrylic resin fine particles. As a result, the excellent thermal stability and low residual strain of the silicone-based resin fine particles are reflected, and the bottoming of the shock absorbing material is further reduced, and the durability is improved. A shock absorbing material that stably exhibits excellent shock absorbing performance over a long period of time can be obtained. In addition, when acrylic resin fine particles are applied, it is possible to make variations in hardness and add functions that take advantage of the degree of freedom in organic molecular design. It is possible to obtain a shock absorbing material that can be used in a wide variety of applications.

It is also preferable that the resin fine particles (B) blended in the impact absorbing resin composition of the impact absorbing material of the present invention be a mixture of two or more kinds of resin fine particles having different components or shapes. As a result, the synergistic action of the polymer viscoelastic resin (A) and the fine resin particles (B) can be designed in various ways, so that it is difficult for the shock absorbing material to bottom out in a thin region of 0.5 mm or less. It is possible to obtain a shock absorbing material whose shock absorbing performance can be variously adjusted.

It is also preferable that the impact-absorbing resin composition of the impact-absorbing material of the present invention further contains hollow resin particles. As a result, the synergistic action between the polymer viscoelastic resin (A) and the resin fine particles (B) can be designed in various ways by the combined action of the resin fine particles (B) and the hollow resin particles, so that the thickness of the resin fine particles is 0.5 mm or less. It is possible to obtain a shock absorbing material capable of variously adjusting the difficulty of bottoming out of the shock absorbing material and the shock absorbing performance in the thin region.

Further, in the impact-absorbing resin composition of the impact-absorbing material of the present invention, the polymeric viscoelastic resin (A) is preferably a silicone-based viscoelastic resin. As a result, excellent thermal stability and low residual strain are reflected, and durability is improved. It is possible to obtain a shock absorbing material that stably exhibits absorption performance over a long period of time.

According to the impact absorbing material of the present invention, the compressive strength Fc (measured in accordance with JIS K6254 D method) as resin fine particles (B) in the polymer viscoelastic resin (A) blended in the impact absorbing resin composition The value obtained by converting the compressive strength Fm at 10% compressive strain as the compressive strength Fc of spherical resin fine particles having a particle size of 10 μm) is dispersed with solid particles having elasticity of 0.06 to 10 MPa, and is used for shock absorption. The cured product or molded product of the resin composition has a hardness of 70 to 170 in terms of penetration (25°C) according to JIS K2207, and the cured product or molded product of the polymer viscoelastic resin (A) has a hardness of JIS Since the needle penetration (25 ° C.) in accordance with K2207 is 100 to 170, dynamic viscoelastic deformation of the polymer viscoelastic resin (A), deformation of the resin fine particles (B), and interparticle distance Due to the synergistic action combined with the action such as change, excellent impact absorption is exhibited, and since the resin fine particles (B) are solid particles with elasticity having a predetermined compressive strength, the polymer Due to the action of moderately suppressing the deformation of the viscoelastic resin (A), it is difficult to bottom out in a thin area of 0.5 mm or less, especially 0.1 mm or more and 0.5 mm or less, and has excellent impact absorption performance. A shock absorbing material is obtained. In addition, by adopting the above-described configuration, in the thin shock absorbing material having a thickness of 0.5 mm or less, the shock absorbing material formed from the base polymer viscoelastic resin (A) alone, or the polymer viscoelastic resin ( Compared to conventional shock absorbers to which hollow resin particles are added to A) or shock absorbers made of a resin foam having closed cells, a shock absorber that is less likely to bottom out and has excellent shock absorbency can be obtained. .

It is a schematic diagram explaining the structure of the impact-absorbing material of this invention.

The impact absorbing material of the present invention is a hardened or molded product of a resin composition for impact absorption, which is obtained by dispersing resin fine particles (B) in a polymer viscoelastic resin (A), and has a thickness of 0.5 mm or less. Compressive strength Fc of resin fine particles (B), which is an absorbent material (compressive strength Fm at 10% compressive strain measured in accordance with JIS K6254 D method, is defined as compressive strength Fc of spherical resin fine particles having a particle size of 10 μm. converted value) is a solid particle having an elasticity of 0.06 to 10 MPa, and the hardness of the cured product or molded product of the polymer viscoelastic resin (A) is the penetration (according to JIS K2207, 25 ° C. ) is 100 to 170, and the hardness of the cured or molded product of the impact absorbing resin composition is 70 to 170 in terms of penetration (according to JIS K2207, 25°C). A detailed description will be given below.

1. Resin composition for impact absorption (1) Polymer viscoelastic resin (A)
The polymer viscoelastic resin (A) that constitutes the resin composition for impact absorption in the present invention is a component for converting impact into heat by dynamic viscoelastic deformation and absorbing it. The polymer viscoelastic resin (A) can be a known viscoelastic resin material that is flexible and has a shock absorbing action. Examples include elastic resins, thermoplastic polymer viscoelastic resins that form thermoplastic viscoelastic bodies such as styrene elastomers, olefin elastomers, and urethane elastomers. Adhesion, durability, transparency, workability, etc. can be selected according to the properties required for the impact absorbing material. Among them, silicone-based viscoelastic resins are suitable from the viewpoint of excellent temperature dependence of hardness and viscoelastic properties, small compression deformation strain, and excellent durability such as heat resistance and chemical resistance. Silicone-based viscoelastic resins that form silicone-based viscoelastic bodies such as elastomers and silicone-based gels can be applied. As the silicone-based viscoelastic resin, it is possible to appropriately select and use a variety of conventionally known and commercially available silicone materials that are generally used. For example, heat curing type, room temperature curing type, energy beam curing type, condensation type or addition type curing mechanism can be used. In addition, the group bonded to the silicon atom is not particularly limited, and examples thereof include alkyl groups such as methyl group, ethyl group and propyl group; cycloalkyl groups such as cyclopentyl group and cyclohexyl group; In addition to aryl groups such as alkenyl groups, phenyl groups and tolyl groups, those groups in which the hydrogen atoms of these groups are partially substituted with other atoms or bonding groups can be mentioned. The silicone-based viscoelastic resin is more preferably an addition reaction type silicone-based viscoelastic resin from the viewpoints of low cost, low cure shrinkage, high molding dimensional accuracy, and excellent productivity including cost.

The hardness of the cured product or molded product of the polymer viscoelastic resin (A) is 100 to 170 at the penetration (25°C) in accordance with JIS K2207, from the viewpoint of shock absorption and handleability such as shape retention. is preferably If the penetration is less than 100, the impact absorbing material may become too hard, resulting in a decrease in impact absorption and flexibility. The above range is preferable because it may be damaged when it is applied or the handling property may be deteriorated.

(2) Resin fine particles (B)
The resin fine particles (B) constituting the impact-absorbing resin composition of the present invention cooperate with the polymer viscoelastic resin (A) to exhibit excellent impact absorption, and the polymer viscoelastic resin (A) It is a constituent element for making it difficult for the shock absorbing material to bottom out due to the effect of moderately suppressing deformation based on the force. Since the fine resin particles (B) are elastic solid particles with a predetermined compressive strength, they are more resistant to impact than closed-cell cells of a foam containing a compressible gas or hollow polymer particles. It has the property of being difficult to deform. Therefore, even a thin shock absorbing material can be prevented from bottoming out, and the moderate deformation of the fine resin particles (B) dispersed in the shock absorbing material allows the polymer viscoelastic resin ( It is possible to exhibit excellent impact absorption in cooperation with A). From the viewpoint of such effects, a compressive strength Fc of 0.06 to 10 MPa obtained by the following formula (1) can be used as an index of the elasticity of the fine resin particles (B). If the compressive strength Fc is less than 0.06 MPa, the resin fine particles (B) may be excessively deformed by the impact, and it may not be possible to sufficiently suppress bottoming of the shock absorbing material. In some cases, the elasticity is too small and the impact absorption in cooperation with the polymeric viscoelastic resin (A) is insufficient. Further, from the viewpoint of suppressing bottoming out of the impact absorbing material due to impact, it is preferable that the compressive strength Fc of the fine resin particles (B) is higher than the compressive strength of the polymer viscoelastic resin (A).

Here, the compressive strength Fc of the fine resin particles (B) is the load speed at which a single fine resin particle (one piece) having a spherical diameter (particle size) of R μm is used as a test specimen and is elastically deformed according to JIS K6254 D method. The compressive stress value at the time when the compressive strain (compressive displacement) reaches 10% of the initial particle size is defined as the compressive strength (measured value) Fm, and the resin fine particles (B) are regarded as spheres, and the following formula is obtained. (1) is used to convert the compressive strength Fc of spherical fine resin particles having a particle size of 10 μm. The reason why the value is calculated in terms of resin fine particles having a spherical diameter of 10 μm is that the above-mentioned effects of the resin fine particles (B) are largely related to the elasticity of the resin fine particles, but the elasticity of the resin fine particles varies depending on the particle size even if the material is the same. This is because spherical resin fine particles with a particle size of 10 μm are used as a standard form and used as a quantitative measure of elasticity. In addition, in Hertz's contact stress theory, the static load in the elastic region is proportional to the particle size of spherical particles to the power of 1/2, so the compressive strength (measured Value) Fm and the compressive strength Fc of spherical resin fine particles with a particle size of 10 μm are equal to the ratio of the particle size of R μm to the power of 1/2 and the particle size of 10 μm to the power of 1/2. This is a formula for calculating the compressive strength Fc of spherical fine resin particles.

In addition, the resin fine particles (B) preferably have an average particle size of 0.5 to 50 μm, more preferably 0.5 to 20 μm, from the viewpoint of more effectively exhibiting the above-mentioned action contributed by the resin fine particles (B). More preferably, 1 to 10 μm is particularly preferable. If the average particle diameter is less than 0.5 μm, the above-mentioned action contributed by the fine resin particles (B) is difficult to manifest, and if it exceeds 50 μm, the elastic force of the fine resin particles (B) becomes dominant. In some cases, when the thickness of the impact absorbing material of the present invention is 0.5 mm or less, particularly in the range of 0.1 mm or more and 0.5 mm or less, sufficient impact absorption may not be obtained. Moreover, when the average particle size exceeds 50 μm, the mechanical strength may be lowered, such as brittleness when used as a shock absorbing material. The average particle diameter of the fine resin particles (B) is obtained by using a laser diffraction/scattering particle size distribution measuring method. An arbitrary number of thousands to tens of thousands of primary particles are measured, and based on the obtained volume-based particle size distribution data, a number-based arithmetic mean value is calculated, and the result is defined as an average particle size.

Further, the shape of the resin fine particles (B) is not particularly limited as long as the above-described effect contributed by the resin fine particles (B) is obtained, but from the viewpoint of uniform dispersibility, etc., a spherical shape is preferable. Further, the material of the resin fine particles (B) is selected according to the dispersibility in the polymer viscoelastic resin (A) and the design of the cooperative action between the polymer viscoelastic resin (A) and the resin fine particles (B). Although known materials can be selected and applied, from the viewpoint of excellent temperature dependence of hardness and viscoelastic properties, small compression deformation strain, and excellent durability such as heat resistance and chemical resistance, silicone resin fine particles are used. Preferably. In addition, from the wide variety of variations that make use of the freedom of organic molecular design, acrylic resin is selected from the perspective of facilitating optimization and diversification of impact absorption performance by combining with polymer viscoelastic resin (A). Fine particles are also preferred.

Further, the fine resin particles (B) may have a coating layer covering the entire surface of the particles. By providing the coating layer on the particle surface, the compressive deformation behavior of the fine resin particles (B) can be changed to diversify the above effects contributed by the fine resin particles (B). Further, the coating layer may have functionality such as dispersibility of the fine resin particles (B) in the polymeric viscoelastic resin (A) and imparting optical properties. In addition, the material, thickness, and physical properties of the coating layer can be appropriately set according to the purpose within a range that does not impair the elasticity of the fine resin particles (B). The coating layer may have the same material and physical properties as those of the fine resin particles (B), or may have a different structure.

In addition, the fine resin particles (B) are dispersed on the surface of the particles in order to improve the dispersibility in the polymer viscoelastic resin (A) and the adhesion between the polymer viscoelastic resin (A) and the resin fine particles (B). A material subjected to surface modification treatment may be applied. As the surface modification treatment, a known method such as a physical surface modification treatment such as corona treatment or excimer treatment, or a chemical surface modification treatment using a silane coupling agent or the like is selected according to the purpose. can be applied.

Further, the resin fine particles (B) may have a configuration in which two or more kinds of resin fine particles having different components (materials) or shapes are combined and mixed. As a result, the synergistic action of the polymer viscoelastic resin (A) and the fine resin particles (B) can be designed in various ways, so that the resistance to bottoming out of the shock absorbing material and the shock absorbing performance can be variously adjusted. When a plurality of resin fine particles of different types are combined, the mixing ratio is not particularly limited as long as the effects of the present invention can be obtained, and can be appropriately set according to the purpose.

In addition, when the impact absorbing material of the present invention is required to have light transmittance, the resin fine particles (B) are selected to have light transmittance and a refractive index close to those of the polymer viscoelastic resin (A). do it. Similarly, the optical properties (light transmittance) of the impact-absorbing resin composition can be appropriately adjusted by selecting the optical properties of the resin fine particles (B).

The mixing ratio of the fine resin particles (B) is preferably 5 to 40 parts by weight, more preferably 15 to 35 parts by weight, and more preferably 20 to 30 parts by weight with respect to 100 parts by weight of the polymer viscoelastic resin (A). Especially preferred. If the blending ratio of the fine resin particles (B) is less than 5 parts by weight, it becomes difficult to obtain the action contributed by the fine resin particles (B), and the cooperation of the polymer viscoelastic resin (A) and the fine resin particles (B). If the amount of the impact absorbing material exceeds 40 parts by weight, the polymer viscoelastic resin (A ) and the synergistic balance between the high molecular weight viscoelastic resin (A) and the fine resin particles (B) deteriorates. be.

(3) Other Compounding Ingredients The impact-absorbing resin composition of the present invention may further contain hollow resin particles as long as the effects of the present invention are not impaired. By using the hollow resin particles together with the fine resin particles (B), it is possible to diversify the impact absorbing properties of the impact absorbing material and reduce the weight thereof. Further, by replacing a part of the fine resin particles (B) with hollow resin particles, flexibility can be improved while maintaining the impact absorbing properties of the impact absorbing material. As the hollow resin particles, known ones can be applied. For example, fine hollow particles which have a shell made of a thermoplastic resin and which contain air or other gas inside and are already in a foamed state or expanded by heat can be mentioned. Although not particularly limited, specific synthetic resin-based micro hollow spheres include "Expancel (registered trademark) 551DE" manufactured by Nippon Philite Co., Ltd., which is a micro hollow sphere made of a copolymer of vinylidene chloride and acrylonitrile. Expancel (registered trademark) 551DE40d42", "Expancel (registered trademark) 092DE120d30" manufactured by Nippon Philite Co., Ltd., and "Matsumoto Microsphere (registered trademark)" manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., and the like. Moreover, "SARAN MICROSPHERES" provided by DOW CHEMICAL can also be used as a polyvinylidene chloride-based resin balloon.

Various additives such as flame retardants, colorants, and mechanical strength improvers may be added to the resin composition for impact absorption of the present invention as long as the effects of the present invention are not impaired. For example, as a flame retardant, expanded graphite, metal hydroxide, magnetite, etc. can be applied, and as a strength reinforcing material, a fine particle filler such as fine particle silica can be applied, and as a coloring agent, various pigments, dyes, etc. can be applied. can do.

(4) Physical Properties of Impact-Absorbing Resin Composition The impact-absorbing resin composition of the present invention has a hardness of 70 to 170 in terms of penetration (25° C.) according to JIS K2207. If the hardness is less than 70, the impact absorbing material formed from the resin composition for impact absorption will be too hard and the impact absorption will be insufficient. Sticking is likely to occur, and the handling property is deteriorated.

2. Impact Absorbing Material As shown schematically in FIG. It is composed of a material and is formed with a thin thickness of 0.5 mm or less. The thickness of the impact absorbing material 10 is preferably 0.1 mm or more so that the effects of the impact absorbing resin composition 1 can be effectively exhibited. If the thickness of the impact absorbing material 10 is less than 0.1 mm, sufficient impact absorption may not be obtained. Also, if the thickness of the shock absorbing material 10 is 0.1 mm or more, excellent shock absorption based on the action of the present invention can be obtained, but it is preferably in the range of 0.1 mm or more and 0.5 mm or less. A thickness of 0.15 to 0.45 mm is more preferable, and a thickness of 0.15 to 0.40 mm is even more preferable. By setting the thickness in this range, it is possible to obtain the shock absorbing material 10 that is significantly superior to the conventional thin shock absorbing material. Also, the shock absorbing material 10 of the present invention can be in the shape of a sheet, a block, or any other desired shape. When the thickness of the shock absorbing material 10 is not uniform and has a shape with different thickness depending on the part, the thickness is 0.5 mm as long as it has a part with a thickness of 0.5 mm or less that functions as the shock absorbing material of the present invention. Even shock absorbers with other portions exceeding 5 mm are included in the technical scope of the shock absorbers of the present invention.

In addition, the impact absorbing material of the present invention has the above-described configuration, so that even if the thickness is formed as thin as 0.5 mm or less, the impact absorbing material formed from the base polymer viscoelastic resin (A) alone material, a conventional shock absorbing material in which hollow resin particles are added to the polymer viscoelastic resin (A), or a shock absorbing material made of a resin foam having closed cells, it is difficult to bottom out, and impact Excellent absorbency. Specifically, the impact absorbing material of the present invention has improved impact absorbing performance by at least 5% or more as compared with the impact absorbing material formed from the base polymer viscoelastic resin (A) alone.

Moreover, the impact absorbing material 10 of the present invention preferably has self-adhesiveness on the surface. By having self-adhesiveness on the surface, there is no need to provide an adhesive layer as a separate structure, so it is possible to create an impact cushioning material with adhesiveness on the surface while maintaining a thin thickness. Easier to install. The strength of the self-adhesiveness of the surface is preferably such that the ball number is 3 to 32 in an inclined ball tack test (inclination angle of 30 degrees) in accordance with JIS Z0237. In addition, the self-adhesiveness may be obtained by utilizing the inherent adhesiveness of the polymer viscoelastic resin (A), or by adding a tackifier to the polymer viscoelastic resin (A). good too.

3. Method for producing impact-absorbing resin composition and impact-absorbing material The impact-absorbing resin composition of the present invention is produced by mixing the polymer viscoelastic resin (A) with the fine resin particles (B) by a known method and dispersing them. can do. Also, the impact absorbing material of the present invention can be obtained by curing or molding the impact absorbing resin composition by a known method. Specifically, when the polymer viscoelastic resin (A) is a thermosetting resin, the uncured liquid polymer viscoelastic resin is blended with the fine resin particles (B) in a predetermined proportion, and mixed with a chemical mixer. or a three-roll type mixer, and the like to obtain an uncured impact-absorbing resin composition. The uncured impact absorbing resin composition is molded into a desired shape and cured by applying energy according to the curing reaction system, such as heat or light, to obtain the impact absorbing material. In the case of a sheet-like impact absorbing material, it can be obtained by forming an uncured impact absorbing resin composition into a sheet, or by coating it on a substrate film and then curing it. In addition, after filling and applying an uncured fluid impact-absorbing resin composition to a desired location to be protected from impact using a dispenser or the like, energy such as heat or light is applied according to the curing reaction system. It may be cured with a heat-resistant material to form a shock absorber directly on the object to be protected.

Further, when the polymer viscoelastic resin (A) is a thermoplastic resin, the polymer viscoelastic resin (A) and the fine resin particles (B) are mixed at a predetermined ratio in a heating kneader such as a twin-screw extruder or a kneader. and heat-kneaded to obtain an impact-absorbing resin composition in which the resin fine particles (B) are dispersed in the polymer viscoelastic resin (A). A shock absorbing material can be obtained by thermoforming this resin composition for shock absorption into a desired shape by known means such as extrusion molding, hot calendar molding, and injection molding. However, if the resin fine particles (B) are also thermoplastic, the resin fine particles may melt and change their shape. The resin fine particles (B) consisting of

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not particularly limited to these examples. The unit of the thickness of the impact absorbing material in Examples and Comparative Examples is expressed in [μm].

Methods for measuring physical properties and evaluating effects in the following examples and comparative examples are as follows.
(1) Hardness (Penetration of cured product of polymer viscoelastic resin (A) and impact-absorbing resin composition)
It was measured by a penetration measurement method (25° C.) based on JIS K2207 “petroleum asphalt”.

(2) Impact absorption rate (impact absorption material)
JIS C60068-2-27 using a pendulum type impact tester PST-300 made by Shinei Test Machinery (weight of pendulum 2 kg, radius of rotation 300 mm and radius of curvature of impact surface 100 mm) Sheet-shaped impact absorbing material and the impact acceleration of the blank when a direct impact was applied to the sample stage without the impact absorbing material, and the impact absorption rate was calculated by the following formula.
Impact absorption rate (%) = (1 - (impact acceleration of impact absorbing material) / (impact acceleration of blank)) x 100

(3) Impact absorption performance improvement rate The impact absorption rate of the impact absorption material formed from the polymer viscoelastic resin (A) alone and the impact absorption material having approximately the same thickness formed from the impact absorption resin composition is The improvement rate of impact absorption performance was calculated by the following formula.
Improvement rate (%) = (Impact absorption rate of impact absorption material formed from resin composition for impact absorption/Impact absorption rate of impact absorption material formed from polymeric viscoelastic resin (A) alone) x 100

(4) Evaluation With respect to the rate of improvement in impact absorption performance, 5% or more was evaluated as acceptable, and less than 5% was evaluated as unacceptable.

Polymer viscoelastic resins (A) used in Examples and Comparative Examples are as shown in Table 1.

The resin fine particles (B) used in Examples and Comparative Examples are as shown in Table 2. The compressive strength Fc, which is an index of the elastic force of the fine resin particles (B) in Table 2, was determined in accordance with JIS K6254 D method using a microcompression tester (MCT-510 manufactured by Shimadzu Corporation) at a load application rate of 0.5. The compressive stress value at the time of reaching 10% compressive strain (compressive displacement) with respect to the initial particle size before compression at 0223 mN / sec is the compressive strength (actual value) Fm, and the spherical diameter ( It was calculated as the compressive strength of resin fine particles with a particle diameter of 10 μm. "Expancel" in Table 2 is a registered trademark.

[Example 1]
No. in Table 1, which is the polymer viscoelastic resin (A). (a) Two-component addition reaction type silicone gel resin (manufactured by Asahi Kasei Wacker Silicone Co., Ltd., model number SLJ-9038, liquid A (main liquid) and liquid B (curing agent-containing liquid) mixed at a weight ratio of 54:46. ) was added to 100 parts by weight of No. in Table 2 as fine resin particles (B). 5 parts by weight of silicone rubber fine particles of A (KMP-597 manufactured by Shin-Etsu Chemical Co., Ltd.) are blended and mixed with a planetary mixer (ACM-5LVT manufactured by Aikosha Seisakusho Co., Ltd.) at 150 rpm for 10 minutes under atmospheric pressure. After mixing at 150 rpm for 10 minutes under a reduced pressure environment of 0.1 MPa, the mixture was defoamed under reduced pressure to obtain an uncured impact absorbing resin composition. Next, the resin composition for impact absorption is applied evenly on a PET film, molded to a thickness of about 200 μm, and then preheated in an oven (WFO-520W manufactured by Tokyo Rika Kikai Co., Ltd.) at 70 ° C. for 1 hour. After that, the resin composition for impact absorption was cured by heating at 100° C. for 3 hours to obtain a sheet-like impact absorption material of Example 1 having a size of 120 mm×120 mm and a thickness of 202 μm. The impact absorption rate of the impact absorbing material of Example 1 was measured. In addition, after filling a cylindrical container having an inner diameter of φ30 mm with a thickness of 30 mm with the impact-absorbing resin composition of Example 1 in an uncured state, it was placed in an oven (WFO-520W manufactured by Tokyo Rika Kikai Co., Ltd.) at 70° C. for 1 hour. The impact-absorbing resin composition was cured by heating at 100° C. for 3 hours to prepare a test piece for hardness evaluation, and the penetration was measured.

[Example 2]
In Example 1, the resin composition for impact absorption of Example 2 was obtained in the same manner as in Example 1, except that the amount of the resin fine particles (B) was changed to 20 parts by weight. A 200 μm sheet-like impact absorbing material of Example 2 was obtained. In the same manner as in Example 1, the penetration of the cured product of the impact absorbing resin composition of Example 2 and the impact absorption rate of the impact absorbing material were measured.

[Example 3]
In Example 1, the resin composition for impact absorption of Example 3 was obtained in the same manner as in Example 1 except that the amount of the resin fine particles (B) was changed to 30 parts by weight, and then the thickness was measured using it. A 203 μm sheet-like impact absorbing material of Example 3 was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 3 and the impact absorption rate of the impact absorbing material were measured.

[Example 4]
In Example 1, the resin composition for impact absorption of Example 4 was obtained in the same manner as in Example 1, except that the amount of the resin fine particles (B) was changed to 40 parts by weight, and then the thickness was measured using it. A 200 μm sheet-like impact absorbing material of Example 4 was obtained. In the same manner as in Example 1, the penetration of the cured product of the impact absorbing resin composition of Example 4 and the impact absorption rate of the impact absorbing material were measured.

[Example 5]
In Example 1, No. in Table 2 was used as the fine resin particles (B). Example 1 except that a spherical silicone rubber (KMP-600 manufactured by Shin-Etsu Chemical Co., Ltd.) having a coating layer made of a silicone resin on the surface of B was used, and the amount of resin fine particles (B) was 20 parts by weight. After obtaining the impact absorbing resin composition of Example 5 in the same manner, a sheet-like impact absorbing material of Example 5 having a thickness of 201 μm was obtained by using it. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 5 and the impact absorption rate of the impact absorbing material were measured.

[Example 6]
In Example 5, the resin composition for impact absorption of Example 6 was obtained in the same manner as in Example 5, except that the amount of the resin fine particles (B) was changed to 30 parts by weight, and then the thickness was measured using it. A 202 μm sheet-like impact absorbing material of Example 6 was obtained. In the same manner as in Example 1, the penetration of the cured product of the impact absorbing resin composition of Example 6 and the impact absorption rate of the impact absorbing material were measured.

[Example 7]
In Example 5, the resin composition for impact absorption of Example 7 was obtained in the same manner as in Example 5, except that the amount of the resin fine particles (B) was changed to 40 parts by weight, and then the thickness was measured using it. A 209 μm sheet-like impact absorbing material of Example 7 was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 7 and the impact absorption rate of the impact absorbing material were measured.

[Example 8]
In Example 1, No. in Table 2 was used as the fine resin particles (B). In the same manner as in Example 1, except that a spherical silicone rubber (KMP-605 manufactured by Shin-Etsu Chemical Co., Ltd.) having a coating layer made of C silicone resin on the surface was used, and the amount was 20 parts by weight. After obtaining the impact-absorbing resin composition of No. 8, a sheet-like impact-absorbing material of Example 8 having a thickness of 199 μm was obtained using it. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 8 and the impact absorption rate of the impact absorbing material were measured.

[Example 9]
In Example 8, the resin composition for impact absorption of Example 9 was obtained in the same manner as in Example 8, except that the amount of the resin fine particles (B) was changed to 30 parts by weight, and then the thickness was measured using it. A 200 μm sheet-like impact absorbing material of Example 9 was obtained. In the same manner as in Example 1, the penetration of the cured product of the impact absorbing resin composition of Example 9 and the impact absorption rate of the impact absorbing material were measured.

[Example 10]
In Example 1, the polymeric viscoelastic resin (A) was No. The impact-absorbing resin composition of Example 10 was prepared in the same manner as in Example 1, except that (c) was changed to a two-component addition-reactive silicone gel (the blending ratio of liquid A and liquid B was 50:50). After that, a sheet-like impact absorbing material of Example 10 having a thickness of 207 μm was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 10 and the impact absorption rate of the impact absorbing material were measured.

[Example 11]
In Example 10, the resin composition for impact absorption of Example 11 was obtained in the same manner as in Example 10, except that the amount of the resin fine particles (B) was changed to 20 parts by weight, and then the thickness was measured using it. A 204 μm sheet-like impact absorbing material of Example 11 was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 11 and the impact absorption rate of the impact absorbing material were measured.

[Example 12]
In Example 10, No. in Table 2 was used as the fine resin particles (B). The impact-absorbing resin composition of Example 12 was obtained in the same manner as in Example 10 except that a spherical silicone rubber having a coating layer made of the silicone resin of B was used on the surface, and then the composition was used to have a thickness of 204 μm. A sheet-like impact absorbing material of Example 12 was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 12 and the impact absorption rate of the impact absorbing material were measured.

[Example 13]
In Example 12, the impact-absorbing resin composition of Example 13 was obtained in the same manner as in Example 12, except that the amount of the fine resin particles (B) was changed to 20 parts by weight. A 204 μm sheet-like impact absorbing material of Example 13 was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 13 and the impact absorption rate of the impact absorbing material were measured.

[Example 14]
In Example 10, No. in Table 2 was used as the fine resin particles (B). The impact-absorbing resin composition of Example 14 was obtained in the same manner as in Example 10 except that a spherical silicone rubber having a coating layer made of the silicone resin of C was used on the surface, and then the composition was used to have a thickness of 207 μm. A sheet-like impact absorbing material of Example 14 was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 14 and the impact absorption rate of the impact absorbing material were measured.

[Example 15]
In Example 14, the impact-absorbing resin composition of Example 15 was obtained in the same manner as in Example 14, except that the amount of the resin fine particles (B) was changed to 20 parts by weight. A 208 μm sheet-like impact absorbing material of Example 15 was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 15 and the impact absorption rate of the impact absorbing material were measured.

[Example 16]
In Example 1, the polymeric viscoelastic resin (A) was No. The procedure of Example 1 was repeated except that (b) the two-part addition reaction type silicone gel (the mixing ratio of liquid A and liquid B was 52:48) and the mixing ratio of fine resin particles (B) was changed to 20 parts by weight. After obtaining the impact-absorbing resin composition of Example 16, a sheet-like impact-absorbing material of Example 16 having a thickness of 200 μm was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 16 and the impact absorption rate of the impact absorbing material were measured.

[Example 17]
In Example 16, No. in Table 2 was used as the fine resin particles (B). A resin composition for impact absorption of Example 17 was obtained in the same manner as in Example 16 except that a spherical silicone rubber having a coating layer made of the silicone resin of C was used on the surface, and then the composition was used to have a thickness of 210 μm. A sheet-like impact absorbing material of Example 17 was obtained. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 17 and the impact absorption rate of the impact absorbing material were measured.

[Example 18]
In Example 1, the polymeric viscoelastic resin (A) was No. The procedure of Example 1 was repeated except that (d) the two-component addition reaction silicone gel (mixing ratio of liquid A and liquid B was 47:53) and the mixing ratio of fine resin particles (B) was changed to 20 parts by weight. After obtaining the impact-absorbing resin composition of Example 18, a sheet-like impact-absorbing material of Example 18 having a thickness of 206 μm was obtained. In the same manner as in Example 1, the penetration of the cured product of the impact absorbing resin composition of Example 18 and the impact absorption rate of the impact absorbing material were measured.

[Example 19]
Using the impact-absorbing resin composition obtained in Example 3, a sheet-like impact-absorbing material of Example 19 having a thickness of 100 μm was obtained. The impact absorption rate of the impact absorbing material of Example 19 was measured.

[Example 20]
Using the impact-absorbing resin composition obtained in Example 3, a sheet-like impact-absorbing material of Example 20 having a thickness of 500 μm was obtained. The impact absorption rate of the impact absorbing material of Example 20 was measured.

[Example 21]
In Example 1, No. in Table 2 was used as the fine resin particles (B). The impact-absorbing resin composition of Example 21 was prepared in the same manner as in Example 1 except that the spherical crosslinked polybutyl methacrylate particles of D (ABX-8 manufactured by Sekisui Chemical Co., Ltd.) were used and the blending amount was 20 parts by weight. After the product was obtained, it was used to obtain a sheet-like impact absorbing material of Example 21 having a thickness of 197 μm. In the same manner as in Example 1, the penetration of the hardened resin composition for impact absorption of Example 21 and the impact absorption rate of the impact absorbing material were measured.

[Example 22]
In Example 21, the resin composition for impact absorption of Example 22 was obtained in the same manner as in Example 21, except that the amount of the resin fine particles (B) was changed to 30 parts by weight. A 200 μm sheet-like impact absorbing material of Example 22 was obtained. In the same manner as in Example 1, the penetration of the cured product of the impact absorbing resin composition of Example 22 and the impact absorption rate of the impact absorbing material were measured.

[Example 23]
In Example 21, the impact-absorbing resin composition of Example 23 was obtained in the same manner as in Example 21, except that the amount of the resin fine particles (B) was changed to 40 parts by weight, and then the thickness was measured using it. A 196 μm sheet-like impact absorbing material of Example 23 was obtained. In the same manner as in Example 1, the penetration of the hardened product of the impact absorbing resin composition of Example 23 and the impact absorption rate of the impact absorbing material were measured.

Table 3 shows the measurement and evaluation results of Examples 1-4, Table 4 shows the measurement and evaluation results of Examples 5-9, Table 5 shows the measurement and evaluation results of Examples 10-15, and Examples 16-18. Table 6 shows the measurement and evaluation results of , Table 7 shows the measurement and evaluation results of Examples 19 and 20, and Table 8 shows the measurement and evaluation results of Examples 21 to 23. In addition, in order to facilitate comparison with each example, among the comparative examples described later, a comparative example of a shock absorbing material having substantially the same thickness formed from a single polymer viscoelastic resin (A) as a base is shown in the table. It was shown to. In the left column of Tables 1 to 8, the compressive strength of the fine resin particles (B) is the compressive strength Fc at 10% compressive strain converted to spherical fine resin particles having a particle size of 10 μm in Table 2.

[Comparative Example 1]
No. in Table 1, which is the polymer viscoelastic resin (A). (a) Two-liquid addition reaction silicone gel resin (manufactured by Asahi Kasei Wacker Silicone Co., Ltd., model number SLJ-9038, liquid A (main liquid) and liquid B (curing agent-containing liquid) blended at a weight ratio of 54:46) was used as the impact-absorbing resin composition of Comparative Example 1, and this impact-absorbing resin composition was applied evenly on a PET film to a thickness of about 0.2 mm, molded, and then placed in an oven (manufactured by Tokyo Rikaki Co., Ltd. WFO-520 W) at 70° C. for 1 hour and then cured by heating at 100° C. for 3 hours to obtain a sheet-like impact absorbing material of Comparative Example 1 having a size of 120 mm×120 mm and a thickness of 197 μm. The impact absorption rate of the impact absorbing material of Comparative Example 1 was measured. In addition, the impact-absorbing resin composition of Comparative Example 1 was filled in an uncured state into a cylindrical container having an inner diameter of φ30 mm and a thickness of 30 mm, and then placed in an oven (WFO-520W manufactured by Tokyo Rika Kikai Co., Ltd.) at 70° C. for 1 hour. After preheating, the composition was cured by heating at 100° C. for 3 hours to prepare a specimen for hardness evaluation, and the penetration was measured.

[Comparative Example 2]
In Comparative Example 1, the polymer viscoelastic resin (A) was No. The impact-absorbing resin composition of Comparative Example 2 was prepared in the same manner as in Comparative Example 1, except that (b) was changed to a two-component addition-reactive silicone gel (the blending ratio of liquid A and liquid B was 52:48). After that, a sheet-like shock absorbing material of Comparative Example 2 having a thickness of 200 μm was obtained by using it. In the same manner as in Example 1 and the like, the penetration of the cured impact-absorbing resin composition of Comparative Example 2 and the impact absorption rate of the impact-absorbing material were measured.

[Comparative Example 3]
In Comparative Example 1, the polymer viscoelastic resin (A) was No. The impact-absorbing resin composition of Comparative Example 3 was prepared in the same manner as in Comparative Example 1, except that (c) was changed to a two-component addition-reactive silicone gel (the blending ratio of liquid A and liquid B was 50:50). After that, a sheet-like impact absorbing material of Comparative Example 3 having a thickness of 206 μm was obtained. In the same manner as in Example 1 and the like, the penetration of the cured impact absorbing resin composition of Comparative Example 3 and the impact absorption rate of the impact absorbing material were measured.

[Comparative Example 4]
In Comparative Example 1, the polymer viscoelastic resin (A) was No. The impact-absorbing resin composition of Comparative Example 4 was prepared in the same manner as in Comparative Example 1, except that (d) was changed to a two-component addition-reactive silicone gel (the blending ratio of liquid A and liquid B was 47:53). After that, a sheet-like impact absorbing material of Comparative Example 4 having a thickness of 197 μm was obtained by using it. In the same manner as in Example 1 and the like, the penetration of the cured impact absorbing resin composition of Comparative Example 4 and the impact absorption rate of the impact absorbing material were measured.

[Comparative Example 5]
In Example 1, the fine resin particles (B) were selected from Nos. In the same manner as in Example 1, except that the fine hollow resin particles (Expancel (registered trademark) 551DE40d42 manufactured by Nippon Philite Co., Ltd.) made of a copolymer of vinylidene chloride and acrylonitrile in F were used, and the blending ratio was 3 parts by weight. After obtaining the impact-absorbing resin composition of Comparative Example 5, a sheet-like impact-absorbing material of Comparative Example 5 having a thickness of 205 μm was obtained. In the same manner as in Example 1 and the like, the penetration of the cured impact-absorbing resin composition of Comparative Example 5 and the impact absorption rate of the impact-absorbing material were measured.

[Comparative Example 6]
In Example 1, the fine resin particles (B) were selected from Nos. Comparative Example 6 was carried out in the same manner as in Example 1 except that the non-elastic spherical crosslinked polybutyl methacrylate particles of E (BM30X-8 manufactured by Sekisui Chemical Co., Ltd.) were used, and the blending amount was 30 parts by weight. After obtaining the impact-absorbing resin composition of No., a sheet-like impact-absorbing material of Comparative Example 6 having a thickness of 204 μm was obtained. In the same manner as in Example 1 and the like, the penetration of the cured impact-absorbing resin composition of Comparative Example 6 and the impact absorption rate of the impact-absorbing material were measured.

[Comparative Example 7]
Using the impact absorbing resin composition of Comparative Example 1, a sheet-like impact absorbing material of Comparative Example 7 having a thickness of 100 μm was obtained. The impact absorption rate of the impact absorbing material of Comparative Example 7 was measured in the same manner as in Example 1 and the like.

[Comparative Example 8]
In Example 18, the resin composition for impact absorption of Comparative Example 8 was obtained in the same manner as in Example 18, except that the amount of the resin fine particles (B) was changed to 40 parts by weight, and then the thickness was measured using it. A 200 μm sheet-like impact absorbing material of Comparative Example 8 was obtained. In the same manner as in Example 1 and the like, the penetration of the cured product of the impact absorbing resin composition of Comparative Example 8 and the impact absorption rate of the impact absorbing material were measured.

[Comparative Example 9]
In Example 21, the polymeric viscoelastic resin (A) was No. Example except that the two-liquid addition reaction type silicone gel (e) (the blending ratio of liquid A and liquid B is 55.5:44.5) and the blending amount of resin fine particles (B) is 5 parts by weight 21 After obtaining the resin composition for impact absorption of Comparative Example 9 in the same manner, a sheet-like impact absorber of Comparative Example 9 having a thickness of 200 μm was obtained by using it. In the same manner as in Example 1 and the like, the penetration of the cured impact absorbing resin composition of Comparative Example 9 and the impact absorption rate of the impact absorbing material were measured.

[Comparative Example 10]
Using the impact absorbing resin composition of Comparative Example 5, a sheet-like impact absorbing material of Comparative Example 10 having a thickness of 100 μm was obtained. The impact absorption rate of the impact absorbing material of Comparative Example 10 was measured in the same manner as in Example 1 and the like.

[Comparative Example 11]
Using the impact absorbing resin composition of Comparative Example 5, a sheet-like impact absorbing material of Comparative Example 11 having a thickness of 500 μm was obtained. The impact absorption rate of the impact absorbing material of Comparative Example 11 was measured in the same manner as in Example 1 and the like.

[Comparative Example 12]
Using the impact absorbing resin composition of Comparative Example 1, a sheet-like impact absorbing material of Comparative Example 12 having a thickness of 500 μm was obtained. The impact absorption rate of the impact absorbing material of Comparative Example 12 was measured in the same manner as in Example 1 and the like.

The evaluation results of Comparative Examples 1 to 4, 7 and 12 are shown in Table 9, the evaluation results of Comparative Examples 5, 6, 8 and 9 are shown in Table 10, and the evaluation results of Comparative Examples 10 and 11 are shown in Table 11. For comparison, Table 10 shows Comparative Examples 1 and 4 of the impact absorbing material formed from the base polymer viscoelastic resin (A) alone, and Table 11 shows Comparative Examples 7 and 12. .

From the results of Examples 1 to 23, the impact absorbing materials having the structure of the present invention contained the impact absorbing resin composition more than the impact absorbing materials of Comparative Examples 1 to 4, 7, and 12, which did not contain fine resin particles. The impact absorption rate is improved in comparison under the same conditions of the hardness of the polymer viscoelastic resin (A) and the thickness of the impact absorbing material. It has been found that a shock absorber with excellent shock absorption in the region is obtained.

Looking at the impact absorption effect for each hardness of the polymer viscoelastic resin (A) constituting the impact absorption resin composition, (1) Examples 1 to 9 and Examples 21 to 23, and Comparative Example 1 (2) Comparison between Examples 10 to 15 and Comparative Example 3, (3) Comparison between Examples 16 and 17 and Comparative Example 2, (4) Comparison between Example 18 and Comparative Example 4, Therefore, the impact absorption rate was improved, and an improvement rate of 5% or more was shown for any hardness of the polymer viscoelastic resin (A).

Further, from the results of Examples 1 to 4, 19 and 20, the smaller the thickness of the shock absorbing material, the smaller the impact absorption rate. Even when it is used as a material, the impact absorbing material according to the present invention shows an improvement rate of more than 27% in impact absorbing performance, and it was found that the impact absorbing property is excellent at the same thickness.

Further, from a comparison between Example 22 and Comparative Example 6, when the compressive strength Fc of the resin fine particles (B) exceeded 12 MPa, the impact absorption rate decreased by about 12%, and Examples 5 to 7, 12, and 13 and Comparative Example 5, if the fine resin particles (B) are hollow particles and have a compressive strength Fc of less than 0.06 MPa, the impact absorption rate is reduced by about 23%. It has been found that a range of 0.06 to 12 MPa is preferred, and a range of 0.08 to 10 MPa is more preferred.

In addition, comparison between Example 19 and Comparative Examples 7 and 10 for a shock absorbing material with a thickness of 100 µm, comparison between Example 20 and Comparative Examples 11 and 12 for a shock absorbing material with a thickness of 500 µm, and comparison between a shock absorbing material with a thickness of 200 µm From the results of the comparison between Example 3 and Comparative Examples 1 and 5, the hollow resin fine particles (B) were added under the same conditions for the hardness of the polymer viscoelastic resin body (A) and the thickness of the shock absorbing material. When used, the impact absorption rate is significantly lowered, and the rate of improvement of the impact absorption rate of the impact absorption material formed from the polymer viscoelastic resin (A) alone is also lowered. is one of the important requirements in the present invention. In addition, when the thickness of the impact absorbing material is 500 μm or less, the addition of the hollow resin particles (B) reduces the impact absorption rate compared to the impact absorbing material formed from the polymer viscoelastic resin (A) alone. The effectiveness of the present invention was confirmed in a region where the thickness is 0.5 mm or less.

Further, from a comparison between Examples 1 to 23 and Comparative Examples 8 and 9, the hardness of the cured product of the impact absorbing resin composition of the present invention is less than 70 in terms of penetration (25°C) according to JIS K2207. If it is more than 170, the shock absorbing material becomes too hard and the impact absorption rate is not sufficiently obtained, and if it exceeds 170, the shock absorbing material becomes too soft and bottoms out due to the impact, resulting in a decrease in the shock absorption rate. It was found that the handling performance deteriorated.

The impact-absorbing material of the present invention has excellent impact-absorbing properties even when the thickness is as thin as 0.5 mm or less. It is suitable for mounting in a narrow space and absorbing impact, and is useful for improving the impact durability of electronic equipment.

REFERENCE SIGNS LIST 1 impact absorbing resin composition 10 impact absorbing material 2 polymer viscoelastic resin 3 fine resin particles

Claims (8)

A shock absorbing material having a thickness of 0.15 to 0.45 mm, comprising a cured product or molded product of a resin composition for shock absorption in which fine resin particles (B) are dispersed in a polymer viscoelastic resin (A). ,
The polymer viscoelastic resin (A) is a silicone-based viscoelastic resin,
The resin fine particles (B) are solid particles having elasticity with a compressive strength Fc of 0.06 to 10 MPa obtained by the following formula (1),

(In formula (1), R is the particle size (μm) of the resin fine particles (B), and Fm is the compressive strength of the resin fine particles (B) at 10% compression strain measured according to JIS K6254 D method ( 10% deformation compressive stress) value.)
The cured product or molded product of the polymer viscoelastic resin (A) has a hardness of 100 to 170 in terms of penetration (according to JIS K2207, 25° C.),
A shock absorbing material characterized in that the cured product or molded product of the impact absorbing resin composition has a hardness of 70 to 170 in terms of penetration (according to JIS K2207, 25°C). 2. The method according to claim 1, wherein the blending ratio of the fine resin particles (B) in the resin composition for impact absorption is 5 to 40 parts by weight with respect to 100 parts by weight of the polymer viscoelastic resin (A). Shock absorber as described. 3. The impact absorbing material according to claim 1, wherein the fine resin particles (B) have an average particle size of 0.5 to 50 μm. 4. The impact absorbing material according to any one of claims 1 to 3, wherein the resin fine particles (B) are spherical. The impact absorbing material according to any one of claims 1 to 4, wherein the resin fine particles (B) are provided with a coating layer covering the entire surface. 6. The impact absorbing material according to claim 1, wherein the resin fine particles (B) are silicone resin fine particles or acrylic resin fine particles. The impact absorbing material according to any one of claims 1 to 6, wherein the resin fine particles (B) are a mixture of two or more kinds of resin fine particles having different components or shapes. The impact absorbing material according to any one of claims 1 to 7, wherein the impact absorbing resin composition further contains hollow resin particles.

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