JP7592829B2 - Resin Molding - Google Patents

Description

This disclosure relates to a resin molded body and a method for manufacturing a resin molded body.

Methods for producing a resin molded body formed by connecting a plurality of expanded beads are known (see, for example, Patent Documents 1 to 3). The resin molded body is generally produced by steam molding using a heating medium such as pressurized steam. The temperature of the heating medium is generally set to be near the melting point of the resin constituting the expanded beads so that the expanded beads can be fused together.
When steam is used as the heating medium, the expanded beads will not fuse to each other unless there is a certain amount of uncrosslinked parts in the expanded beads. In other words, the degree of crosslinking of the expanded beads cannot be made very high. Therefore, it is difficult to produce a resin molded product with a high degree of crosslinking by using expanded beads with a low degree of crosslinking. Of course, even if expanded beads with a high degree of crosslinking are used, a resin molded product with a high degree of crosslinking can be produced by connecting the expanded beads to each other using a binder. However, the binder affects the performance of the resin molded product, such as heat resistance and compressive strength.
As described above, steam molding of expanded beads with a high degree of crosslinking is difficult, and the use of a binder is also undesirable, so that currently, resin molded articles using expanded beads have a low degree of crosslinking.

JP 2018-44118 A Special Publication No. 2008-533289 Special Publication No. 2-502649

As described above, currently available resin moldings have a low degree of crosslinking, and therefore do not necessarily have sufficient compression set performance, and improvements have been required.
The present disclosure has been made in view of the above circumstances, and has an object to provide a resin molded article having a high degree of crosslinking and good compression set. The present disclosure can be realized in the following aspects.

[1] A resin molded article formed by connecting a plurality of foamed particles,
The expanded beads are produced using raw materials including a thermoplastic resin, a silane coupling agent in an amount of 0.4 parts by mass or more and 3.5 parts by mass or less relative to 100 parts by mass of the thermoplastic resin, a cell breaker, and a foaming agent;
The expanded beads contain a crosslinked thermoplastic resin,
The crosslinked thermoplastic resin has a crosslinked structure in which the thermoplastic resin is crosslinked by a siloxane bond,
The expanded beads have holes on a surface thereof,
The foamed particles are bonded to each other by siloxane bonds,
The resin molded article has a gel fraction of 50% or more and 99% or less.

The resin molded body of the present disclosure has a high degree of crosslinking and low compression set.

1 is a schematic diagram of a resin molded body according to the present disclosure. FIG. 2 is a schematic diagram of an expanded bead. FIG. 2 is a schematic diagram of an expanded bead. FIG. 1 is an explanatory diagram illustrating a conventional manufacturing method. FIG. 1 is an explanatory diagram illustrating a conventional manufacturing method. FIG. 1 is an explanatory diagram illustrating a conventional manufacturing method. FIG. 2 is an explanatory diagram illustrating a manufacturing method according to the present disclosure.

Here, a preferred example of the present disclosure is given.
[2] The resin molded body according to [1], having a hardness of 5 or more and 30 or less on the Asker C scale.
If the hardness falls within this range, it is highly practical.
[3] The resin molded body according to [1] or [2], having a compressive strength of 35 kPa or more and 100 kPa or less.
If the compressive strength is within this range, it is highly practical.
[4] The resin molded article according to any one of [1] to [3], having a compression set of 5% or more and 50% or less.
If the compression set is within this range, the composition is highly practical.
[5] A first step of producing expanded particles from a raw material including a thermoplastic resin, a silane coupling agent in an amount of 0.4 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the thermoplastic resin, a cell breaker, and a foaming agent;
a second step of placing the expanded beads in a mold and heating the molded product with a heating medium containing moisture to produce a resin molded product in which the expanded beads are bonded together;
A method for producing a resin molded body comprising the steps of:
This manufacturing method makes it possible to produce a resin molded article having a high degree of crosslinking and low compression set.
[6] The gel fraction of the expanded beads is 20% or more and 70% or less,
The method for producing a resin molded body according to [5], wherein a gel fraction of the resin molded body is greater than a gel fraction of the expanded beads and is within a range of 50% to 99%.
This manufacturing method makes it possible to produce a resin molded article having a high degree of crosslinking and low compression set.
[7] The method for producing a resin molded product according to [5] or [6], wherein in the heating step, the foamed particles are bonded to each other via siloxane bonds.
This manufacturing method does not use a binder, so that it is possible to manufacture a resin molded article having good heat resistance, compressive strength, etc.
The present invention will be described in detail below. Note that, when a range is indicated as "x to y", both x and y are included in the range unless otherwise specified.

1. Resin molded body 1
The resin molded body 1 is formed by connecting a plurality of expanded beads 3 (see FIG. 1). The expanded beads 3 are manufactured using raw materials including a thermoplastic resin, a silane coupling agent in an amount of 0.4 parts by mass to 3.5 parts by mass to 100 parts by mass of the thermoplastic resin, a cell breaker, and a foaming agent. The expanded beads contain a crosslinked thermoplastic resin. The crosslinked thermoplastic resin has a crosslinked structure in which the thermoplastic resin is crosslinked by a siloxane bond. The expanded beads have holes on the surface. The individual expanded beads are bonded to each other by a siloxane bond. The gel fraction of the resin molded body is 50% to 99%.

(1) Raw materials for the expanded particles 3 (1.1) Thermoplastic resin The thermoplastic resin is preferably at least one selected from the group consisting of olefin thermoplastic elastomer (TPO), polypropylene, polyethylene, ABS resin, polyvinyl chloride, thermoplastic rubber crosslinked body (TPV), styrene thermoplastic elastomer (TPS), TPEE (polyester thermoplastic elastomer), and urethane thermoplastic elastomer (TPU). Olefin thermoplastic elastomer (TPO) is preferred from the viewpoints of being widely distributed, inexpensive, and having a wide range of selectable hardness and fluidity.

As the olefin-based thermoplastic elastomer (TPO), for example, an ethylene-α-olefin copolymer can be used.
The ethylene-α-olefin copolymer is a copolymer having structural units derived from ethylene and structural units derived from at least one α-olefin selected from α-olefins having 4 to 10 carbon atoms. The ethylene-α-olefin copolymer may be any of a random copolymer, a block copolymer, and a graft copolymer.

Specific examples of α-olefins having 4 to 10 carbon atoms used in ethylene-α-olefin copolymers include 1-octene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-decene, and α-olefins having a cyclic structure, with 1-octene and 1-butene being preferred.

The content of structural units derived from at least one α-olefin selected from α-olefins having 4 to 10 carbon atoms contained in the ethylene-α-olefin copolymer is preferably 1% by mass to 49% by mass, more preferably 1% by mass to 30% by mass, and even more preferably 1% by mass to 20% by mass (the total mass of the ethylene-α-olefin copolymer is taken as 100% by mass).

Specific examples of ethylene-α-olefin copolymers include ethylene-1-octene copolymers, ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-decene copolymers, ethylene-(3-methyl-1-butene) copolymers, and copolymers of ethylene and α-olefins having a cyclic structure.

An example of an ethylene-α-olefin copolymer is ENGAGE (trademark) manufactured by Dow Chemical Japan Ltd.

The melt flow rate (MFR) of the thermoplastic resin is not particularly limited.
From the viewpoint of extrusion moldability, the melt flow rate (MFR) of the thermoplastic resin is preferably 0.5 to 10 g/10 min, as measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238.

(1.2) Silane coupling agent The silane coupling agent is not particularly limited. The silane coupling agent is used as a crosslinking agent. The silane coupling agent is preferably one having an alkoxysilyl group. Examples of the silane coupling agent having an alkoxysilyl group include an alkoxysilyl compound having a vinyl group, an alkoxysilyl compound having an epoxy group, and an alkoxysilyl compound having an acrylic group or a methacrylic group, and one or more types can be used in combination. In particular, an alkoxysilyl compound having a vinyl group is more preferable because it has good reactivity with thermoplastic resins and is inexpensive. Specific examples of the alkoxysilyl compound having a vinyl group include vinyltrimethoxysilane and vinyltriethoxysilane.

The mixing ratio of the silane coupling agent is 0.4 parts by mass or more, preferably 0.75 parts by mass or more, and more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the base resin (thermoplastic resin), from the viewpoint of obtaining a resin molded body 1 with suppressed compression set. The upper limit is 3.5 parts by mass or less, preferably 2.5 parts by mass or less, and more preferably 1.5 parts by mass or less, from the viewpoint of preventing the expanded particles 3 from becoming brittle and breaking. Therefore, the mixing ratio of the silane coupling agent is 0.4 parts by mass or more and 3.5 parts by mass or less, preferably 0.75 parts by mass or more and 2.0 parts by mass or less, and more preferably 1.0 parts by mass or more and 1.5 parts by mass or less.

(1.3) Foaming agent The foaming agent is preferably a pyrolysis type foaming agent that decomposes by heating to generate gas, and is not particularly limited. For example, one or more of azodicarbonamide, 2,2'-azobisisobutyronitrile, diazoaminobenzene, benzenesulfonylhydrazide, benzene-1,3-sulfonylhydrazide, diphenyloxide-4,4'-disulfonylhydrazide, 4,4'-oxybisbenzenesulfonylhydrazide, paratoluenesulfonylhydrazide, N,N'-dinitrosopentamethylenetetramine, N,N'-dinitroso-N,N'-dimethylphthalamide, terephthalazide, p-t-butylbenzazide, sodium bicarbonate, ammonium bicarbonate, etc. are used. In particular, azodicarbonamide and 4,4'-oxybisbenzenesulfonylhydrazide are preferred.
The mixing ratio of the foaming agent is preferably from 2 to 6 parts by mass, and more preferably from 3 to 5 parts by mass, per 100 parts by mass of the base resin (thermoplastic resin).

(1.4) Cell opener The raw material contains a cell opener. The cell opener may be used alone or in combination of two or more.
As the foam breaker, for example, one or a combination of two or more monoglycerides and diglycerides of linear saturated or unsaturated fatty acids having 30 or less carbon atoms (more preferably 8 to 24 carbon atoms) can be used. Examples of linear saturated or unsaturated fatty acids include butyric acid (butanoic acid), caproic acid (hexanoic acid), caprylic acid (octanoic acid), capric acid (decanoic acid), lauric acid (dodecanoic acid), myristic acid (tetradecanoic acid), palmitic acid (hexadecanoic acid), stearic acid (octadecanoic acid), arachidonic acid (eicosanoic acid), behenic acid (docosanoic acid), lignoceric acid (tetracosanoic acid), palmitoleic acid ((Z)-9-hexadecenoic acid), oleic acid ((Z)-9-hexadecenoic acid), elaidic acid ((E)-9-octadecenoic acid), cisvaccenic acid ((Z)-11-octadecenoic acid), linoleic acid ((9Z,1 Suitable examples of the foam breaker include α-linolenic acid ((9Z,12Z,15Z)-9,12,15-octadecadienoic acid), γ-linolenic acid ((6Z,9Z,12Z)-6,9,12-octadecatrienoic acid), di-homo-γ-linolenic acid ((8Z,11Z,14Z)-8,11,14-eicosatrienoic acid), arachidonic acid ((5Z,8Z,11Z,14Z)-5,8,11,14-eicosatetraenoic acid), erucic acid ((Z)-13-docosenoic acid), nervonic acid ((Z)-15-tetracosenoic acid), ricinoleic acid, hydroxystearic acid, undecylenic acid, and mixtures thereof. As the foam breaker, for example, glycerin monostearate is preferably used.
The mixing ratio of the defoamer is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.25 parts by mass or more, relative to 100 parts by mass of the base resin (thermoplastic resin), in terms of the lower limit, from the viewpoint of obtaining the desired expanded particles without shrinking during expansion. The upper limit is preferably 5 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 1.5 parts by mass or less, in terms of obtaining the desired expanded particles without shrinking during expansion. Therefore, the mixing ratio of the defoamer is preferably 0.05 parts by mass or more and 5 parts by mass or less, more preferably 0.1 parts by mass or more and 3.0 parts by mass or less, and even more preferably 0.25 parts by mass or more and 1.5 parts by mass or less.

(1.5) Reaction initiator The raw material may contain a reaction initiator. Examples of reaction initiators include dialkyl peroxides, diacyl peroxides, and alkyl peresters, and one or more of these may be used in combination. In particular, dialkyl peroxides are preferred in terms of reactivity and cost. Specific examples include dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.
The mixing ratio of the reaction initiator is not particularly limited. From the viewpoint of sufficiently promoting the grafting reaction of the silane coupling agent, the mixing ratio of the reaction initiator is preferably 0.01 parts by mass or more and 1.0 parts by mass or less, and more preferably 0.1 parts by mass or more and 0.075 parts by mass or less, relative to 100 parts by mass of the base resin (thermoplastic resin).

(1.6) Reaction Terminator In the production of the expanded beads 3, a reaction terminator (radical scavenger) is usually used. Examples of reaction terminators include compounds capable of scavenging radicals, such as phenolic antioxidants and hindered amine light stabilizers, and one or more types can be used in combination. Hindered amine light stabilizers are more preferred because the hindered amine light stabilizers themselves are colorless and have excellent radical scavenging properties. When using a phenolic antioxidant, there are grades in which the phenolic antioxidant itself is colored, and even if the grade is not colored, there are grades that become colored during processing with a kneader, etc., so it is preferable to select a grade that does not become colored even when processed with a kneader, etc. If a colored grade or a grade that becomes colored during processing is used, it is preferable to use an amount that does not affect the colorability of the thermoplastic resin.
The mixing ratio of the reaction terminator is preferably from 0.01 to 0.3 parts by mass, and more preferably from 0.05 to 0.2 parts by mass, per 100 parts by mass of the base resin (thermoplastic resin).

(1.7) Catalyst (Silanol Crosslinking Promotion Catalyst)
It is preferable to blend a catalyst in the raw material. Examples of the catalyst include dibutyltin and fatty acid amide, and one or more of them can be used in combination. The blending ratio of the catalyst is preferably 0.01 parts by mass or more and 0.1 parts by mass or less, and more preferably 0.02 parts by mass or more and 0.06 parts by mass or less, per 100 parts by mass of the base resin (thermoplastic resin).

(1.8) Additives If necessary, additives that are usually used in resins, such as light stabilizers (hindered amine light stabilizers), antioxidants (phenolic antioxidants, etc.), processing aids such as lubricants and release agents (metal soaps such as erucic acid amide and calcium stearate), softeners, colorants, fillers, conductive agents, flame retardants, etc., can be added to the raw materials within the range that does not impair the desired physical properties of the expanded beads 3.

(2) Expanded beads 3
The number of the expanded beads 3 constituting the resin molded body 1 is not particularly limited, and can be appropriately selected depending on the application of the resin molded body 1, etc.
The expanded beads 3 contain a crosslinked thermoplastic resin having a crosslinked structure in which a thermoplastic resin is crosslinked by a siloxane bond (-Si-O-Si-). The content of the crosslinked thermoplastic resin in the expanded beads 3 is not particularly limited. The content of the crosslinked thermoplastic resin in the expanded beads 3 is preferably 90% by mass or more, more preferably 95% by mass or more. The content of the crosslinked thermoplastic resin may be 100% by mass.
The expanded beads 3 have pores on their surface. The diameter of the pores is not particularly limited. The diameter of the pores can be determined as follows. A sample is cut, and an enlarged photograph of the cross section is taken with an electron microscope. The area of each pore present within a certain area of the enlarged photograph is measured, and an equivalent circle diameter is calculated from the obtained area to determine the diameter of each pore. The diameters of each pore thus obtained are then arithmetically averaged to determine the average diameter of the pores. From the viewpoint of shrink suppression, the average diameter of the pores thus determined is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less, and even more preferably 3 μm or more and 5 μm or less.
The expanded beads 3 are bonded to each other by siloxane bonds.
Moreover, it is preferable that the expanded beads 3 have an interconnected structure in which a plurality of pores are interconnected (see FIG. 2). For comparison with FIG. 2, FIG. 3 shows a case in which no interconnection occurs (closed cell case).

(3) Gel Fraction of Resin Molded Body 1 From the viewpoint of reducing compression set, the gel fraction of the resin molded body 1 is, with respect to the lower limit, 50% or more, preferably 70% or more, and more preferably 85% or more. The gel fraction of the resin molded body 1 is 50% or more and 99% or less, preferably 70% or more and 99% or less, and more preferably 85% or more and 99% or less.
The gel fraction in this specification is a value measured based on JIS K 6796/ISO-15875-2:2003 (refluxed in xylene for 8 hours, then dried and measured).

(4) Effects of the Resin Molded Product 1 of the Present Embodiment The resin molded product 1 of the present embodiment is useful because it has a high degree of crosslinking and a low compression set.

2. Method for Manufacturing Resin Molded Body 1 The method for manufacturing the resin molded body 1 includes a first step and a second step.

(1) First Step In this step, the expanded beads 3 are produced from raw materials including a thermoplastic resin, a silane coupling agent in an amount of 0.4 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the thermoplastic resin, a cell breaker, and a blowing agent.
The mixing ratio of the defoamer is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.25 parts by mass or more, relative to 100 parts by mass of the base resin (thermoplastic resin), in terms of the lower limit, from the viewpoint of obtaining the desired expanded particles without shrinking during expansion. The upper limit is preferably 5 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 1.5 parts by mass or less, in terms of obtaining the desired expanded particles without shrinking during expansion. Therefore, the mixing ratio of the defoamer is preferably 0.05 parts by mass or more and 5 parts by mass or less, more preferably 0.1 parts by mass or more and 3.0 parts by mass or less, and even more preferably 0.25 parts by mass or more and 1.5 parts by mass or less.
A suitable example of this process will be described. A thermoplastic resin, a silane coupling agent, a peroxide (a reaction initiator), and a cell breaker are melted and kneaded. During this process, the alkoxysilyl group of the silane coupling agent is grafted onto the thermoplastic elastomer using radicals generated from the peroxide.
Next, the thermoplastic resin having an alkoxysilyl group, the chemical foaming agent (such as azodicarbonamide (ADCA)), and the defoamer are melt-kneaded. At this time, _CO2 gas generated by the decomposition reaction of the chemical foaming agent in the extruder is dispersed in the thermoplastic resin having an alkoxysilyl group, and a high pressure state is maintained.
When the kneaded material is discharged from the extruder die, the pressure is reduced to atmospheric pressure, and the _CO2 gas dispersed in the thermoplastic resin having an alkoxysilyl group starts to expand (foam).
When or after the _CO2 gas starts expanding, the surface of the expanded thermoplastic resin particles and the defoamer dispersed therein reduce the interfacial tension.
When the cell opener reduces the interfacial tension, the cells become smaller and the coalescence of the cells can be suppressed. Furthermore, the addition of the cell opener facilitates the breaking of the cells, and voids are formed on the surface and/or inside of the expanded beads 3 (interconnection).
The formation of voids reduces the pressure difference between the inside and outside, making the expanded beads 3 less likely to shrink.
In this manner, the expanded beads 3 are produced. The expanded beads 3 may be cured in a high-temperature and high-humidity heating furnace.
The gel fraction of the expanded beads 3 is 20% or more and 70% or less. By setting the gel fraction of the expanded beads 3 in this range, unreacted alkoxysilyl groups remain. Then, in the heating step described below, the remaining alkoxysilyl groups are reacted to form siloxane bonds, which bond the expanded beads 3 together, thereby producing a resin molded product 1 with a high degree of cross-linking.

(2) Second Step In this step, the expanded beads 3 are placed in a mold and heated with a heating medium containing moisture to form a resin molded body 1 in which the expanded beads 3 are linked together.
A preferred example of this process will be described.
The expanded beads 3 are filled into a mold having a structure through which a high-temperature heating medium (steam, pressurized steam, superheated steam, etc.) can flow.
The compression ratio is changed by compressing the foamed beads 3 from their filling height in the mold to their height during secondary molding.
Once compressed to the height required for secondary molding, a heating medium (for example, 120°C to 250°C) is poured into the mold.
The alkoxysilyl groups of the expanded beads 3 react with the moisture in the heating medium to form siloxane bonds between the expanded beads 3 and also inside the expanded beads 3 .
The formation of siloxane bonds bonds the expanded beads 3 together and promotes cross-linking of the expanded beads 3, thereby producing the resin molded body 1.
The gel fraction of the resin molding 1 is greater than the gel fraction of the expanded beads 3 and is within the range of 50% or more and 99% or less, more preferably within the range of 70% or more and 99% or less, and even more preferably within the range of 85% or more and 99% or less.

(3) Differences Between the Conventional Manufacturing Method and the Manufacturing Method of the Present Embodiment Here, the concepts of the differences between the conventional manufacturing method and the manufacturing method of the present embodiment will be described with reference to FIGS.
As shown in FIG. 4, the expanded beads 3A, 3A which are cross-linked to a low degree can be fused together by thermal expansion.
As shown in FIG. 5, the moderately crosslinked expanded particles 3B, 3B can also be fused by thermal expansion.
However, as shown in FIG. 6, highly cross-linked expanded beads 3C, 3C do not fuse together even when heated.
Under these circumstances, it has been difficult to produce a resin molded article in which a plurality of highly crosslinked expanded beads 3 are connected to one another.
In the present disclosure, as shown in Fig. 7, steam is applied to the moderately crosslinked expanded beads 3D, 3D having alkoxysilyl groups remaining therein, and the silanol crosslinking reaction between the expanded beads 3D, 3D is utilized to bond the expanded beads 3D, 3D to each other while proceeding with the silanol crosslinking reaction inside each of the expanded beads 3D, 3D. In this manner, in the manufacturing method of the present embodiment, a resin molded product in which a plurality of highly crosslinked expanded beads 3 are connected is produced.

(4) Effects of the Manufacturing Method of the Resin Molded Article 1 According to the manufacturing method of this embodiment, it is possible to manufacture a resin molded article 1 having a high degree of crosslinking and low compression set.

The present disclosure will be explained in more detail by showing examples. However, the present disclosure is not limited to these examples, and can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

The various measurements in the following explanation were taken using the test methods listed below. The overall evaluation was performed as follows:

1. Test Method (1) Gel Fraction The gel fraction is a value measured in accordance with JIS K 6796/ISO-15875-2:2003 (refluxed in xylene for 8 hours, then dried and measured).

(2) Compression set The compression set was measured in accordance with JIS K6262:2013 (23°C x 22h, 25% compression). JIS K6262:2013 is a standard corresponding to ISO 815-1 and ISO 815-2.

Permanent compression strain (%) = 100 x (t ₀ - t ₁ )/(t ₀ - t ₂ )
t ₀ : thickness of test piece (mm)
_t1 : thickness of test piece after 30 min of release (mm)
_t2 : thickness of test piece at 25% compression (spacer thickness) (mm)

(3) Compressive strength The compressive strength was measured in accordance with JIS K6767:1999 (compressive stress after 20 seconds at 25% compression). JIS K6767:1999 is a standard corresponding to ISO 3386-1.

(4) Asker C hardness The Asker C hardness was measured in accordance with JIS K7312:1996 (test piece: 50×50×t20 mm, hardness immediately after contact).

(5) Interconnectivity The interconnectivity was calculated by counting the number of pores of 2 μm or more in the outermost 5 mm of the cross section of an expanded bead. The cross section of the expanded bead was observed under an electron microscope at a magnification of 1000 times. The number of pores was counted for five expanded beads, and the average value was calculated.

(6) Compression Ratio The compression ratio was calculated using the following formula.
Compression ratio (%)=100×(h ₀ −h ₁ )/h _0
h0 : Height when filled (mm)
_h1 : Height when compressed (mm)

(7) Moldability: Evaluated as follows.
A: A resin molding in which a plurality of foamed beads were connected was obtained.
B: The foamed particles were not bonded to each other, and a resin molding was not obtained.

(8) Overall Evaluation The moldability, compression set, and compressive strength of the resin molded product were evaluated comprehensively. The overall evaluation was specifically performed as follows.
C: Compression set is 50% or more, or the moldability of the resin molding is poor. B: Compression set is less than 50%, and the compression strength is 50 kPa to less than 60 kPa. A: Compression set is less than 50%, and the compression strength is less than 50 kPa.

2. Preparation of Expanded Beads Using the raw materials shown in Table 1 below, various expanded beads were prepared according to the compositions shown in Tables 2, 3, and 4.
Example 1 and Comparative Example 1 were aged under the conditions shown in Table 2.

3. Molding and Evaluation of Resin Molded Body Using the expanded beads produced in the Examples and Comparative Examples, each resin molded body was molded and evaluated according to the description in the above-mentioned section "Heating step for molding resin molded body 1."
The resin moldings of Examples 1 to 7 all had a high degree of crosslinking and small compression set. The overall evaluation of Examples 1 to 7 was either A or B, which was good.
In Comparative Example 1, the crosslinking proceeded excessively due to excessive curing, and the gel fraction of the expanded beads was extremely high at 95%. Therefore, in Comparative Example 1, the expanded beads were not bonded to each other, and a resin molded product could not be obtained.
In Comparative Example 2, since no cell opener was added, the resin particles shrunk and no expanded beads were obtained. Therefore, in Comparative Example 2, a resin molded article could not be produced.
In Comparative Example 3, the amount of the silane coupling agent was too small at 0.2 parts by mass, and the gel fraction of the expanded beads was very low at 3%. Therefore, in Comparative Example 4, the gel fraction of the resin molded article was low at 27%, and the compression set was large.
In Comparative Example 4, the amount of the silane coupling agent was as large as 5 parts by mass, so that the graft reaction was excessive, causing severe resin deterioration and making it difficult to flow, and a resin molded article could not be produced.
In Comparative Example 5, no silane coupling agent was blended, and the compression set of the resin molded article was large.

1... resin molded body 3... foamed particles 5... steam

Claims (4)

A resin molded article formed by connecting a plurality of foamed particles,
The expanded beads contain a crosslinked thermoplastic resin,
The crosslinked thermoplastic resin has a crosslinked structure in which the thermoplastic resin is crosslinked by a siloxane bond,
The foamed particles are bonded to each other by siloxane bonds,
The resin molded article has a gel fraction of 95% or more and 99% or less. A resin molded article formed by connecting a plurality of foamed particles,
The expanded beads contain a crosslinked thermoplastic resin,
The crosslinked thermoplastic resin has a crosslinked structure in which the thermoplastic resin is crosslinked by a siloxane bond,
The foamed particles are bonded to each other by siloxane bonds,
The resin molded body has a gel fraction of 50% or more and 99% or less,
A resin molded product having a hardness of 5 or more and 30 or less on the Asker C scale. A resin molded article formed by connecting a plurality of foamed particles,
The expanded beads contain a crosslinked thermoplastic resin,
The crosslinked thermoplastic resin has a crosslinked structure in which the thermoplastic resin is crosslinked by a siloxane bond,
The foamed particles are bonded to each other by siloxane bonds,
The resin molded body has a gel fraction of 50% or more and 99% or less,
A resin molded product having a compressive strength according to JIS K6767:1999 (compressive stress after 20 seconds at 25% compression) of 35 kPa or more and 100 kPa or less. A resin molded article formed by connecting a plurality of foamed particles,
The expanded beads contain a crosslinked thermoplastic resin,
The crosslinked thermoplastic resin has a crosslinked structure in which the thermoplastic resin is crosslinked by a siloxane bond,
The foamed particles are bonded to each other by siloxane bonds,
The resin molded body has a gel fraction of 50% or more and 99% or less,
A resin molded product having a compression set calculated by the following formula in accordance with JIS K6262:2013 (23 ° C. × 22 h, 25% compression) of 5% or more and 12% or less.

Compression set (%) = 100 x (t ₀ - t ₁ )/(t ₀ - t ₂ )
t ₀ : thickness of test piece (mm)
_t1 : thickness of test piece after 30 min of release (mm)
_t2 : thickness of test piece at 25% compression (spacer thickness) (mm)

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