Silicone molded body, silicone composite, and method for producing silicone molded body

Abstract

To provide a silicone molded body of small thickness change and excellent durability by reducing the content of cyclic siloxane of a low molecular weight derived from silicone.MEANS FOR ACHIEVING THE PURPOSE: A silicone molded body containing cyclic siloxane has a content of the cyclic siloxane of 4-20 units of 7,400 mass ppm or less in the silicone molded body.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a silicone molded article, a silicone composite, and a method for producing a silicone molded article that can be suitably used as various release materials, etc., for use in molding ICs, passive components, semiconductors, etc. that are incorporated into electric and electronic products, components for display and touch panel related products, components for LED lighting products, components for measuring movement and biological function, etc. [Background technology]

[0002] Silicones, such as silicone rubber and silicone resin, and in particular, millable silicone rubber, have traditionally been used as release agents and anti-slip materials (hereinafter referred to as "sealing materials") due to their excellent heat resistance and electrical properties.

[0003] However, when an attempt is made to use a sheet made of a simple silicone such as silicone rubber as a release material for press molding, the rubber product will deform, resulting in poor assembly dimensional accuracy and wrinkles, making it difficult to work with. In order to solve the above problems, the composite integration of silicone rubber and plastic film has been considered. This not only improves workability such as wrinkles and adhesion, but also makes it easier to obtain long composites, which can be used for efficient roll-to-roll manufacturing.

[0004] One method of compounding is to compound a pre-crosslinked silicone rubber alone with a plastic film via an adhesive, or to compound via an adhesive layer by laminating double-sided tape or applying an adhesive, etc. In this case, an adhesive or adhesive for silicone rubber is usually used, but it is necessary to apply the adhesive or adhesive separately, which causes inconveniences such as high processing costs and difficulty in obtaining a long composite.

[0005] Furthermore, in order to solve such problems, a method has been studied in which a silicone primer is applied to a plastic film, a silicone uncrosslinked rubber is laminated thereon, and then thermal crosslinking is performed to simultaneously integrate the silicone rubber. However, when the plastic film is mainly composed of a polyester resin, the adhesion between the silicone primer and the plastic film is poor, and the resulting composite is prone to problems such as peeling.

[0006] Furthermore, if the plastic film has low heat resistance, this method cannot be applied because heat is applied during crosslinking of the silicone rubber. Furthermore, there is a problem that the obtained composite tends to curl due to the large difference in thermal expansion between the plastic film and the silicone rubber. In addition, since the thickness precision is insufficient, when the plastic film is stacked or accumulated in roll form, as the amount accumulated increases, wrinkles and folds occur and the original shape is not restored, making it difficult to use as a release material.

[0007] As a silicone rubber composite that can solve the above-mentioned problems, Patent Document 1 proposes a silicone rubber composite in which a primer layer and a thin film layer that has high affinity for the primer layer and contains a silicone resin are formed in that order on at least one side of a film whose main component is a polyester resin, and a silicone rubber layer made of a silicone elastomer resin having a specific hardness is formed, and the film and the silicone rubber layer are integrated together. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 11-20082 Summary of the Invention [Problem to be solved by the invention]

[0009] However, when the silicone rubber composite of Patent Document 1 is used repeatedly as a release material in the press molding of electrical and electronic product components, depending on the conditions, the thickness of the silicone composite may change, the cushioning properties as a release material may not be sufficiently maintained, or the number of repeated uses may be limited, so specific improvements were desired. In addition, silicones such as silicone rubber contain cyclic siloxanes, but cyclic siloxane tetramers to hexamers (D4-6 siloxanes) are included in the 19th SVHC (Substances of Very High Concern) list of the European REACH Regulation and are designated as substances of very high concern, so silicones with lower amounts of low molecular weight cyclic siloxanes are desired. Furthermore, when electrical and electronic product parts are press-molded, cyclic siloxanes may adhere to the electrical and electronic product parts, contaminating the contacts of the conductive parts and causing electrical conductivity defects. Furthermore, the inventors' investigations have revealed that even if the content of D4-6 siloxane is reduced, repeated use under high temperatures and pressures such as press molding will result in bleeding of relatively high molecular weight cyclic siloxanes, specifically 7-20 mer cyclic siloxanes (D7-20 siloxanes), and adhering to molded products during processes such as press molding, which may cause problems when such molded products are used as actual products.

[0010] The present invention was made under these circumstances, and has an object to provide a silicone molded article, a silicone composite, and a method for producing a silicone molded article, which can reduce the content of low-molecular-weight cyclic siloxane derived from silicone and have excellent durability and little change in thickness. [Means for solving the problem]

[0011] As a result of extensive investigations, the present inventors have found that it is possible to reduce the amount of low molecular weight cyclic siloxanes, and by reducing the amount of cyclic siloxanes in this manner, they have surprisingly succeeded in obtaining a silicone molded article that is highly durable and exhibits minimal change in thickness, and a silicone composite using the same, thereby completing the present invention.

[0012] That is, the present invention provides the following [1] to

[23] . [1] A silicone molded article containing a cyclic siloxane, wherein the content of 4-20 monomers of cyclic siloxane in the silicone molded article is 7,400 ppm by mass or less. [2] The silicone molded article according to [1], wherein the content of cyclic siloxane pentamer in the silicone molded article is 700 ppm by mass or less. [3] The silicone molded article according to [1] or [2], wherein the content of cyclic siloxane heptamers to 20-mers in the silicone molded article is 6,400 ppm by mass or less. [4] The silicone molded article according to any one of [1] to [3], wherein the content of cyclic siloxane decamers to 20-mers in the silicone molded article is 5,300 ppm by mass or less. [5] The silicone molded article according to any one of [1] to [4], wherein the content of cyclic siloxane dodecamer to cyclodecamer in the silicone molded article is 4600 ppm by mass or less. [6] The silicone molded article according to any one of [1] to [5], wherein the content of cyclic siloxane 15-20 monomers in the silicone molded article is 3,300 ppm by mass or less. [7] The silicone molded article according to any one of [1] to [6], wherein the content of cyclic siloxane heptamer to 20-mer in the silicone molded article is 2100 ppm by mass or less. [8] The silicone molded article according to any one of [1] to [7], which contains a silicone elastomer resin. [9] The silicone molded article according to any one of [1] to [8], which is used for press molding, vacuum molding, or pressure molding.

[10] The silicone molded article according to any one of [1] to [9], which is used as a release material, a cushioning material, or an anti-slip material in molding.

[11] A silicone composite comprising a base layer laminated on at least one surface of the silicone molded article according to any one of [1] to

[10] .

[12] A silicone composite having a base layer on at least one surface of a silicone molded article containing a cyclic siloxane, wherein the content of 15-20 monomers of cyclic siloxane in the silicone composite is 2,330 ppm by mass or less.

[13] The silicone composite according to

[12] , wherein the content of cyclic siloxane 17-20 monomers in the silicone composite is 1,530 ppm by mass or less.

[14] The silicone composite according to any one of

[11] to

[13] , wherein the base layer contains a polyester resin.

[15] The silicone composite according to any one of

[12] to

[14] , wherein the silicone molded body contains a silicone elastomer resin.

[16] The silicone composite according to any one of

[11] to

[15] , which is used for press molding, vacuum molding, or pressure molding.

[17] The silicone composite according to any one of

[11] to

[16] , which is used as a mold release material, a cushioning material, or an anti-slip material in molding.

[18] A carrier film comprising the silicone molded article according to any one of [1] to

[10] or the silicone composite according to any one of

[11] to

[17] .

[19] A protective film comprising the silicone molded article according to any one of [1] to

[10] or the silicone composite according to any one of

[11] to

[17] .

[20] A method for producing a silicone molded article, comprising the steps of: subjecting uncrosslinked silicone to a heat treatment; and subjecting the silicone to a crosslinking treatment.

[21] A method for producing a silicone molded product according to

[20] , comprising the steps of: molding uncrosslinked silicone into a plate-like molded product; heat treating the plate-like molded product; plasticizing the heat-treated plate-like molded product and then extruding it into a film or sheet; and crosslinking the film or sheet obtained.

[22] The method for producing a silicone molded article according to

[21] , wherein the plate-like molded article has a thickness of 10 mm or less.

[23] The method for producing a silicone molded article according to any one of

[20] to

[22] , wherein the heat treatment temperature in the heat treatment step is 100 to 280°C. Effect of the Invention

[0013] According to the present invention, it is possible to provide a silicone molded article that has a reduced amount of low-molecular-weight cyclic siloxane and exhibits little change in thickness and excellent durability, and a silicone composite using the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, examples of embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below as long as the gist of the present invention is not exceeded.

[0015] In the present invention, the term "main component" includes the implication that other components may be contained within a range that does not impair the function of the main component, unless otherwise specified. In this case, the content ratio of the main component is not specified, but the main component (when two or more components have the same content ratio, the total amount of these) accounts for 50 mass% or more of the composition, preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, and particularly preferably 90 mass% or more (including 100 mass%).

[0016] In the present invention, "cyclic siloxane" refers to a compound having a cyclic molecular structure skeleton formed by siloxane bonds. In general, it refers to a cyclic dimethyl type having a dimethylsiloxane unit in which a silicon atom having two methyl groups on the silicon atom is bonded to an oxygen atom, but it is not limited thereto and also includes those in which a silicon atom having a group other than a methyl group, such as a hydrogen atom or an ethyl group, is bonded to an oxygen atom.

[0017] In the present invention, when expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably larger than X" and "preferably smaller than Y". In the present invention, when it is expressed as "X or more" (X is any number), it includes the meaning of "preferably larger than X" unless otherwise specified, and when it is expressed as "Y or less" (Y is any number), it includes the meaning of "preferably smaller than Y" unless otherwise specified.

[0018] Furthermore, a "sheet" generally refers to a thin, flat product whose thickness is small relative to its length and width, as defined in JIS, and a "film" generally refers to a thin, flat product whose thickness is extremely small relative to its length and width, and whose maximum thickness is arbitrarily limited, and which is usually supplied in the form of a roll (JIS K6900:1994). However, the boundary between "sheet" and "film" is unclear, and since there is no need to distinguish between the two in the present invention, in the context of the present invention, when it is referred to as "film," it is intended to include "sheet," and when it is referred to as "sheet," it is intended to include "film."

[0019] In the present invention, "ppm by mass" may be abbreviated simply as "ppm".

[0020] <Silicone molded body> A silicone molded article (hereinafter, sometimes referred to as "the present molded article") as one embodiment of the present invention will be described.

[0021] The raw material components of the silicone molded body are not particularly limited as long as they contain silicone, but for example, it is preferable that they contain silicone having a siloxane skeleton represented by the following formula (1). In the following formula (1), in addition to polydimethylsiloxane in which all of the R in the formula are methyl groups, various polydimethylsiloxanes in which some of the methyl groups are substituted with one or more of other alkyl groups, vinyl groups, phenyl groups, fluoroalkyl groups, etc. can also be appropriately selected. In addition, n in the formula is a positive number of 1 or more, preferably 3 to 5000.

[0022] [ka]

[0023] Of the above silicones, silicone elastomer resins are preferred, and it is even more preferred that the raw material component of the silicone molded article contains silicone elastomer resins as the main component. Preferred examples of the silicone elastomer resin include silicone elastomer resins containing polydimethylsiloxane as a main component.

[0024] From the viewpoint of adjusting the compression set, it is also preferable that the polydimethylsiloxane contains a vinyl group. When vinyl groups are contained, the content of vinyl groups relative to the total amount of polydimethylsiloxane is preferably 0.05 to 5 mol%, more preferably 0.5 to 4 mol%, and even more preferably 1 to 3 mol%. If the content of vinyl groups is equal to or more than the lower limit, it becomes easier to adjust the crosslink density of the silicone elastomer resin, and it tends to be easier to obtain a silicone elastomer resin having a desired compression set. On the other hand, if the content is equal to or less than the upper limit, it is preferable because the silicone elastomer resin does not harden excessively. As another method for obtaining the desired compression set, it is also preferable to select a polydimethylsiloxane that does not contain vinyl groups and is mainly composed of methyl groups, from the viewpoint of adjusting the crosslinking points.

[0025] The compression set is preferably 75% or less, more preferably 60% or less, even more preferably 50% or less, particularly preferably 40% or less, and most preferably 30% or less. By keeping the compression set at the upper limit or less, the thickness of the silicone molded article tends to be less likely to change even when it is repeatedly used during press molding, etc., and sufficient cushioning properties tend to be maintained, resulting in excellent durability, which is preferable. The compression set is measured according to JIS K6249:2003 after treating at 180° C. for 22 hours and then leaving to stand at room temperature (23° C.) for 30 minutes.

[0026] The raw material components of the silicone molded body preferably have a type A durometer hardness of 20 or more, more preferably 30 or more, even more preferably 40 or more, particularly preferably 50 or more, and most preferably 60 or more. The type A durometer hardness is preferably 90 or less, more preferably 85 or less. By making the type A durometer hardness equal to or greater than the lower limit, the thickness of the silicone molded body tends not to change even when repeatedly used during press molding, etc., and sufficient cushioning properties are maintained, resulting in excellent durability, and the tackiness of the surface of the silicone molded body tends to be suppressed, leading to improved handleability. On the other hand, by making the type A durometer hardness equal to or less than the upper limit, the conformability and adhesion to the pressed product during press molding, etc., tends to be improved. The type A durometer hardness can be measured in accordance with JIS K6253-3:2012.

[0027] Preferred methods for adjusting the Type A durometer hardness include, for example, adjusting the amount of filler such as silica that is mixed as a reinforcing material into the raw material silicone, appropriately selecting the type of raw material silicone, and, specifically, using a resin having phenyl groups and adjusting the amount of phenyl groups.

[0028] As such silicone elastomer resin, commercially available products can be used, such as Millable silicone compound manufactured by Shin-Etsu Chemical Co., Ltd. and Millable silicone rubber manufactured by Momentive Performance Materials, Inc.

[0029] Here, the raw material components of the silicone molded article may contain various additives that impart functionality as an elastomer, in addition to reinforcing fillers such as fumed silica, precipitated silica, diatomaceous earth, and quartz powder, various processing aids, and heat resistance improvers, etc. These may be used alone or in combination of two or more kinds. Examples of the additives include a flame retardant, a heat dissipating filler, and a conductive filler.

[0030] In the silicone molded article of the present invention, the content of 4-20 monomers of cyclic siloxane in the silicone molded article is 7400 ppm or less, preferably 7000 ppm or less, more preferably 6800 ppm or less, even more preferably 6000 ppm or less, and particularly preferably 5000 ppm or less. By reducing the content of 4-20-mers, so-called low molecular weight cyclic siloxanes, it is possible to prevent the low molecular weight cyclic siloxanes derived from silicone from precipitating during product manufacturing such as press molding, and adhering to and contaminating the molding machine and the resulting molded products, etc. Furthermore, by reducing the amount of low molecular weight cyclic siloxanes, the silicone molded product itself becomes harder, and even with repeated use, there is little change in thickness, the cushioning properties as a mold release agent can be adequately maintained, and it becomes highly durable. From the viewpoint of moldability and processability, the lower limit is preferably 100 ppm, more preferably 300 ppm, and even more preferably 500 ppm.

[0031] In addition, if a silicone molded body contains a large amount of low molecular weight cyclic siloxane, for example, when it is used as an electric / electronic product component, the low molecular weight cyclic siloxane will come out to the surface of the silicone molded body, and may contaminate the contacts of the conductive part during subsequent wiring processing, etc., causing a conduction failure. Specifically, when a plasma called an arc is generated when the contacts of the conductive part are opened and closed, if the silicone molded body contains a large amount of low molecular weight cyclic siloxane, the gasified low molecular weight cyclic siloxane will adhere to the contacts due to the heat generated when the arc is generated. This causes silicone to precipitate on the contact surface, which may cause a conduction failure. In addition, when it is used as a protective film or carrier film, the low molecular weight cyclic siloxane may precipitate due to heating, pressure, etc. in the usage environment, and may adhere to the product and cause contamination. Because the silicone molded article of the present invention has a cyclic siloxane tetramer-20mer content below the upper limit mentioned above, it is believed that problems such as contact contamination, poor conduction, and product contamination are less likely to occur.

[0032] The content of the cyclic siloxane pentamer in the silicone molded article is preferably 700 ppm or less, more preferably 550 ppm or less, even more preferably 400 ppm or less, particularly preferably 300 ppm or less, and especially preferably 200 ppm or less.Since the pentamer is particularly prone to volatilization or bleeding due to its low molecular weight among low molecular weight cyclic siloxanes, by reducing the content of the pentamer, the above-mentioned problems caused by the volatilization or bleeding of the low molecular weight cyclic siloxane tend to be suppressed.

[0033] The content of cyclic siloxane heptamers to 20-mers in the silicone molded article is preferably 6400 ppm or less, more preferably 5300 ppm or less of cyclic siloxane decamers, more preferably 4600 ppm or less of cyclic siloxane dodeca-20-mers, particularly preferably 3300 ppm or less of cyclic siloxane 15-20-mers, and particularly preferably 2100 ppm or less of cyclic siloxane 17-20-mers. Among low molecular weight cyclic siloxanes, those with a large number of cyclic siloxane subunits tend to be less prone to volatilization or bleeding out, but tend to bleed out due to long-term use or repeated use, and there is a tendency to be able to suppress bleeding out in this case. As a result, even if used for a long time or repeatedly, there is a tendency to suppress the deterioration of function due to bleeding and the contamination of molding machines, molded products, etc.

[0034] Furthermore, the content of cyclic siloxane heptamers to 20-mers in the silicone molded article is more preferably 6000 ppm or less, further preferably 5300 ppm or less, particularly preferably 4700 ppm or less, and particularly preferably 4300 ppm or less. The content of cyclic siloxane decamers to 20-mers in the silicone molded article is more preferably 5000 ppm or less, further preferably 4500 ppm or less, particularly preferably 4300 ppm or less, and particularly preferably 4000 ppm or less. The content of cyclic siloxane 12-20 monomers in the silicone molded article is more preferably 4300 ppm or less, further preferably 4100 ppm or less, particularly preferably 4000 ppm or less, and particularly preferably 3900 ppm or less. The content of cyclic siloxane 15-20 monomers in the silicone molded article is more preferably 3200 ppm or less, and even more preferably 3100 ppm or less.

[0035] The content of low molecular weight cyclic siloxanes in silicone molded products can be reduced by appropriately selecting silicone raw materials with a low content of low molecular weight cyclic siloxanes, by volatilizing the low molecular weight cyclic siloxanes by heat treatment during the production process of the silicone molded products, by extracting the low molecular weight cyclic siloxanes with a solvent such as acetone, or by performing roll kneading, trimix kneading, or planetary kneading under reduced pressure or vacuum, etc.

[0036] The thickness of the silicone molded article may be appropriately selected depending on the application, but is preferably 3 mm or less, more preferably 1 mm or less, even more preferably 800 μm or less, particularly preferably 600 μm or less, and especially preferably 400 μm or less. From the viewpoints of appropriate elasticity, long-term use, and repeated use, the lower limit is preferably 10 μm, more preferably 30 μm, even more preferably 50 μm, and particularly preferably 80 μm.

[0037] Contained in silicone molding 1 H's T 2His preferably 56 ms or less, more preferably 55.5 ms or less, even more preferably 55 ms or less, particularly preferably 54.5 ms or less, and most preferably 54 ms or less. The lower limit is preferably 50 ms. 2H The T of this molded product can be evaluated for relatively large molecular motion and can be used as a standard index for molecular crosslinking and resin softness. The longer the time, the higher the molecular motion and the softer the resin. 2H The shorter the time, the harder the material is, and as a result, the smaller the change in thickness is, and the greater the tendency for durability to be. Said T 2H was measured by spin echo spectroscopy using solid-state NMR. 2H ( 1 It is obtained by measuring the 1H spin-spin relaxation time.

[0038] <Method of manufacturing silicone molded body> The method for producing a silicone molded body is not particularly limited, but when a crosslinkable silicone raw material is used, it is preferable to have a step of subjecting uncrosslinked silicone to a heat treatment (hereinafter referred to as a "heat treatment step") and a step of subjecting the silicone to a crosslinking treatment (hereinafter referred to as a "crosslinking treatment step"). Since the heat treatment can be performed at once at the stage of uncrosslinked silicone raw material, and the process can be shortened, it is more preferable to pass through the crosslinking treatment step after the heat treatment step. Furthermore, the step of molding the uncrosslinked silicone raw material into a silicone molded body (hereinafter referred to as a "molding step") may be performed before or after the heat treatment step, but since the effect of reducing low molecular weight cyclic siloxane is large, it is more preferable to perform the crosslinking treatment after the heat treatment step and after the molding step. Such steps will be specifically described below.

[0039] The present invention preferably includes the heat treatment step, which volatilizes the low molecular weight cyclic siloxane, thereby reducing the content of low molecular weight cyclic siloxane in the obtained silicone molded article.

[0040] The stage for carrying out the heat treatment is not particularly limited. The uncrosslinked silicone may be heat-treated beforehand before molding the silicone molded article, or the uncrosslinked silicone molded article may be molded first and then heat-treated, but from the standpoint of the effect of reducing low-molecular-weight cyclic siloxanes, it is preferable to heat-treat the uncrosslinked silicone before molding the silicone molded article.

[0041] In the heat treatment step, the silicone raw material in an uncrosslinked state may be directly subjected to heat treatment, but it is preferable to heat the plate-shaped molded body after molding it into a plate-shaped shape from the viewpoint of the effect of reducing low molecular weight cyclic siloxane. The thickness of the uncrosslinked plate-shaped molded body (before heat treatment) is preferably 10 mm or less, more preferably 6 mm or less, even more preferably 5 mm or less, particularly preferably 4 mm or less, and especially preferably 3.5 mm or less. If it is the above thickness, low molecular weight cyclic siloxane is volatilized, and the content of low molecular weight cyclic siloxane in the obtained silicone molded body tends to be more easily reduced. In addition, from the viewpoint of handling and processing amount, the lower limit is preferably 0.5 mm, more preferably 1 mm.

[0042] The heating temperature in the heat treatment step is preferably 100 to 280° C., more preferably 130 to 250° C., and even more preferably 160 to 230° C. By keeping the temperature within this range, the silicone is less likely to deteriorate, and the content of low-molecular-weight cyclic siloxane in the silicone molded product tends to be further reduced.

[0043] The heating time in the heat treatment step is preferably 0.1 to 30 hours, more preferably 0.3 to 20 hours, even more preferably 0.5 to 10 hours, particularly preferably 1 to 9 hours, and most preferably 1.5 to 8 hours. By keeping the heating time within this range, the silicone is less likely to deteriorate, and the content of low-molecular-weight cyclic siloxane in the silicone molded product tends to be effectively reduced.

[0044] In the molding step, the silicone raw material in an uncrosslinked state is molded into an uncrosslinked silicone molded body by extrusion molding, injection molding, calendar molding, press molding, etc. In the heat treatment step, when the silicone raw material is once molded into a plate-like shape or the like and then heated, it is preferable to plasticize the plate-like molded body after the heat treatment by a method such as roll kneading, trimix kneading, or planetary kneading, and then mold the silicone molded body again. In addition, the shape of such a molded body is not particularly limited, but it is preferable to mold it into a film or sheet shape from the viewpoints of productivity and processability when forming a silicone composite as described below.

[0045] Next, in the crosslinking treatment step, the silicone raw material in the uncrosslinked state is crosslinked to obtain the silicone molded article of the present invention. Examples of means for crosslinking silicone include a method in which a curing catalyst, curing agent, crosslinking agent, etc. is added in advance to the silicone raw material to be used, and then cured by heat, light such as ultraviolet light, moisture in the air, etc., and a method in which crosslinking is performed by exposure to radiation.

[0046] In particular, the silicone molded article is preferably a radiation-cured product cured by irradiation with radiation, since curing by irradiation with radiation is preferred because there is no risk of loss of heat resistance or light resistance reliability due to residues of catalysts or crosslinking agents.

[0047] Examples of radiation include electron beams, X-rays, and gamma rays. These radiations are widely used industrially, can be easily used, and are energy-efficient. Among them, gamma rays are preferably used because they have almost no absorption loss and are highly transparent.

[0048] The dose of gamma rays can be appropriately selected and determined depending on the type of resin, the amount of crosslinking groups, and the type of radiation source. In the present molded product, for example, the dose of gamma rays is preferably 20 to 150 kGy, more preferably 30 to 120 kGy, even more preferably 40 to 110 kGy, and particularly preferably 50 to 100 kGy. If the dose of exposure is equal to or greater than the lower limit, the silicone molded product can be sufficiently crosslinked, and as a result, the desired compression set and durometer hardness tend to be easily obtained. On the other hand, if the dose of exposure is equal to or less than the upper limit, the increase in low molecular weight cyclic siloxane components due to decomposition reaction tends to be suppressed.

[0049] In the present invention, from the viewpoint of achieving both the effect of reducing low molecular weight cyclic siloxanes and productivity, it is particularly preferable to have, in this order, the steps of molding uncrosslinked silicone raw material into a plate-like molded body, subjecting the plate-like molded body to a heat treatment, plasticizing the plate-like molded body after the heat treatment and then extruding it into a film or sheet, and subjecting the obtained film or sheet to a crosslinking treatment.

[0050] <Silicone complex> Next, a silicone composite using the silicone molded article (hereinafter also referred to as "the present composite") will be described as another embodiment of the present invention.

[0051] Because the present composite has a base material layer laminated on at least one surface of the silicone molded article, it is less prone to wrinkling or bending, and improves the productivity of molded articles when used as a release material for, for example, press molding, vacuum molding, pressure molding, etc.

[0052] The content of cyclic siloxane 15-20-mers in the silicone composite is 2330 ppm or less, preferably 2300 ppm or less, more preferably 2270 ppm or less, even more preferably 2250 ppm or less, and particularly preferably 2230 ppm or less. The content of cyclic siloxane 17-20-mers is preferably 1530 ppm or less, more preferably 1510 ppm or less. Among low molecular weight cyclic siloxanes, those with a large number of cyclic siloxane subunits tend not to volatilize or bleed out, but they tend to bleed out after long-term or repeated use, and this bleed-out can be suppressed, which prevents the deterioration of functionality and contamination of molded products due to bleeding, even when the product is used repeatedly as a cushioning material for press molding, for example. From the viewpoint of moldability and processability, the lower limit is preferably 100 ppm, more preferably 300 ppm, and even more preferably 500 ppm.

[0053] The content of low molecular weight cyclic siloxanes in the silicone composite can be reduced by appropriately selecting silicone raw materials with a low content of low molecular weight cyclic siloxanes, by carrying out a heat treatment during the production process of the silicone molded product or silicone composite to volatilize the low molecular weight cyclic siloxanes, by extracting the low molecular weight cyclic siloxanes with a solvent such as acetone, or by carrying out roll kneading, trimix kneading, or planetary kneading under reduced pressure or vacuum, etc.

[0054] The thickness of the silicone composite may be appropriately selected depending on the application, but is preferably 5 mm or less, more preferably 3 mm or less, even more preferably 1.5 mm or less, particularly preferably 1 mm or less, and especially preferably 800 μm or less. In addition, from the viewpoints of easy attainment of appropriate elasticity and good handleability, the lower limit is preferably 30 μm, more preferably 50 μm, even more preferably 100 μm, and particularly preferably 150 μm.

[0055] With regard to the change in thickness of the silicone composite due to pressing, as measured by the following measurement method, from the viewpoint of durability, it is preferably 4.4 μm or less, more preferably 4.1 μm or less, even more preferably 3.8 μm or less, and particularly preferably 3.6 μm or less.

[0056] The thickness change was measured using a press machine (manufactured by Imoto Manufacturing Co., Ltd., product name BIGHEART) at room temperature (23°C) and a press pressure of 500 kg / cm. 2 The thickness before pressing and the thickness after three pressings are measured under the above conditions, and the thickness change is calculated according to the following formula. The number of samples is two or more, and the average value is calculated as the thickness change. [Formula]|T3-T0| T0: Thickness before pressing T3: Thickness after 3 pressings

[0057] Included in the silicone molded body of the silicone composite 1 H's T 2H is preferably 56 ms or less, more preferably 55.5 ms or less, even more preferably 55 ms or less, particularly preferably 54.5 ms or less, and most preferably 54 ms or less. The lower limit is preferably 50 ms. 2H can be used to evaluate relatively large molecular motion and can be used as a standard index of molecular cross-linking and resin softness. The longer the time, the higher the molecular motion and the softer the resin. 2H The shorter the time, the harder the material is, and as a result, the smaller the change in thickness is, and the greater the tendency for durability to be. Said T 2H was measured by spin echo spectroscopy using solid-state NMR. 2H ( 1 It is obtained by measuring the 1H spin-spin relaxation time.

[0058] [Silicone molded body (silicone layer)] This composite contains a silicone molded body (silicone layer) and a base layer, and the raw materials for such a silicone molded body (silicone layer) are the same as those for the silicone molded body of the present invention described above.

[0059] [Base material layer] The material of the base layer is not particularly limited, and examples thereof include olefin resins, styrene resins, polyester resins, polycarbonate resins, polyamide resins, polyetherimide resins, polyphenylene sulfide resins, polyphenylene ether resins, polyaryl ether ketone resins, liquid crystal polymer resins, polyimide resins, etc. From the viewpoints of heat resistance and mechanical strength, it is preferable for the base layer to contain a polyester resin, and it is more preferable for the base layer to contain a polyester resin as a main component.

[0060] Among polyester resins, it is preferable to use crystalline polyester resins, and examples of crystalline polyester resins include polyethylene terephthalate and polyethylene naphthalate. Among them, polyethylene terephthalate is preferable from the viewpoint of heat resistance, film stiffness, smoothness, ease of commercial availability, and adhesion to the silicone layer. These may be used alone or in combination of two or more kinds.

[0061] The base layer may also contain additives such as ultraviolet absorbers, light stabilizers, antioxidants, plasticizers, nucleating agents, lubricants, pigments, dyes, etc., within the scope of not impairing the effects of the present invention. From the viewpoint of mechanical strength, it is preferably stretched at least uniaxially, and more preferably stretched biaxially.

[0062] The thickness of the substrate layer is preferably 10 to 350 μm, more preferably 15 to 300 μm, and even more preferably 20 to 250 μm. By making the thickness equal to or greater than the lower limit, the occurrence of wrinkles and the like tends to be sufficiently suppressed when a silicone layer or other layer is laminated on the surface. On the other hand, by making the thickness equal to or less than the upper limit, the substrate layer does not become too hard, and therefore it tends to be easier to apply an undercoat layer, which will be described later.

[0063] In addition, in the present composite, it is preferable to provide an undercoat layer and / or a thin film layer between the substrate layer and the silicone molded body, and the layer structure of such a silicone composite is formed by laminating and integrating the substrate layer / undercoat layer / thin film layer / silicone molded body (silicone layer) in this order. For convenience, the substrate layer will be described below as layer A, the undercoat layer as layer B, the thin film layer as layer C, and the silicone molded body (silicone layer) as layer D.

[0064] [Undercoat layer (B layer)] The undercoat layer (B layer) preferably contains an amorphous polymer, more preferably contains an amorphous polymer as a main component, and is provided on one side of the base layer (A layer). By using the undercoat layer (B layer), the thin film layer (C layer) tends to be formed uniformly.

[0065] The amorphous polymer is not particularly limited as long as it can be uniformly applied to the base layer (A layer), and may be appropriately selected from polymers that are substantially non-crystalline, such as polyurethane resins, acrylic resins, amorphous polyester resins, etc. These may be used alone or in combination of two or more kinds. Specific examples include polyurethane resins in which polyester resins and / or polyether resins are polymerized into a linear chain with urethane bonds, etc., acrylic resins made of copolymers of acrylic acid and / or methacrylic acid ester, and copolymer polyester resins in which the acid component or glycol component is made of two or more monomers. These amorphous polymers are applied to form a thin film, so they are usually used in a state diluted with an organic solvent, or in a state adjusted to an appropriate concentration by emulsifying or solubilizing in water.

[0066] The undercoat layer (B layer) may have a crosslinked structure for the purpose of improving heat resistance and solvent resistance, in which case the amorphous polymer has a crosslinkable functional group such as a carboxyl group, a hydroxyl group, or an amino group in the main chain or side chain, and the crosslinking agent is appropriately selected from polyisocyanate, melamine, polyfunctional epoxy resin, metal compound, etc. In addition to the crosslinking agent, the coating liquid may contain a leveling agent such as a surfactant, an anti-blocking agent such as silica, a thickener, etc. These may be used alone or in combination of two or more kinds.

[0067] The thickness of the undercoat layer (layer B) is preferably from 0.01 to 5 μm, more preferably from 0.05 to 4 μm, and even more preferably from 0.1 to 3 μm. If the thickness of the undercoat layer (B layer) is equal to or greater than the lower limit, the thickness can be easily adjusted, and the adhesion to the thin film layer (C layer) described later tends to be good, which is preferable. If the thickness is equal to or less than the upper limit, the undercoat layer (B layer) can be more easily applied, which is preferable.

[0068] [Thin film layer (C layer)] The thin film layer (C layer) is further provided on the undercoat layer (B layer). The thin film layer (C layer) preferably contains a silicone resin, more preferably contains a silicone resin as a main component, and is particularly preferably one that has a high affinity with the undercoat layer (B layer) and forms a crosslinked coating upon heating or UV irradiation after application, or one that forms a crosslinked coating simultaneously with crosslinking of the silicone layer (D layer).

[0069] Examples of silicone resins that can be used in the thin film layer (C layer) include addition type silicone resins, condensation type silicone resins, UV curing type silicone resins, etc., and among them, condensation type silicone resins are preferred because they can effectively obtain the effects of the present invention. These can be used alone or in combination of two or more kinds.

[0070] Examples of addition type silicone resins include those obtained by mixing polymethylhydrogensiloxane as a crosslinking agent with polydimethylsiloxane containing vinyl groups as a base polymer, and reacting and curing the mixture in the presence of a platinum catalyst. Condensation type silicone resins include those obtained by mixing polydimethylsiloxane containing silanol groups at the terminals as the base polymer with polymethylhydrogensiloxane as a crosslinking agent, and curing by heating in the presence of an organotin catalyst. Examples of UV-curable silicone resins include those that use polydimethylsiloxane containing acryloyl groups or methacryloyl groups as the base polymer, those that use polydimethylsiloxane containing mercapto groups and vinyl groups as the base polymer, the above-mentioned addition type silicone resins, or those that use polydimethylsiloxane containing epoxy groups that cure by a cationic curing mechanism as the base polymer, etc., which are blended with a photopolymerization initiator and cured by irradiating with UV light.

[0071] In addition, the thin film layer (C layer) preferably contains an additive such as a silane coupling agent for the purpose of increasing the affinity with the undercoat layer (B layer). A silane coupling agent that satisfies this purpose is a compound represented by the general formula YRSiX3, where Y is an organic functional group such as a vinyl group, an epoxy group, an amino group, or a mercapto group, R is an alkylene group such as methylene, ethylene, or propylene, and X is a hydrolyzable functional group such as a methoxy group or an ethoxy group, or an alkyl group.

[0072] Examples of the silane coupling agent include vinyltriethoxysilane, vinyltrimethoxysilane, γ-glycidylpropyltrimethoxysilane, γ-glycidylpropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, etc. These may be used alone or in combination of two or more.

[0073] The thickness of the thin film layer (C layer) after drying the solvent is preferably 0.01 to 1 μm, more preferably 0.03 to 0.7 μm, and even more preferably 0.05 to 0.5 μm. If the thickness is equal to or greater than the lower limit, a cured film of uniform thickness is obtained, and the adhesive strength with the silicone layer (D layer) tends to be sufficient. In addition, since the silicone resin of the thin film layer (C layer) composition generally does not have a very strong film strength, cohesive failure tends to occur in the thin film layer (C layer) when evaluating the peel strength of this composite. However, if the thickness is equal to or less than the upper limit, the cohesive failure of the thin film layer (C layer) is suppressed, and the silicone composite tends to have sufficient strength.

[0074] [Layer structure] The laminated structure of the silicone composite of the present invention essentially comprises Layer A and Layer D, but as described above, it is preferable that the layers are laminated in the order of Layer A / Layer B / Layer C / Layer D and integrated together. In addition, a layer other than Layer B and Layer C may be present between Layer A and Layer D. If necessary, another layer such as a protective layer may be laminated on the surface of the silicone layer (Layer D). Furthermore, when antistatic performance is required, an antistatic layer may be laminated on the outermost surface of the composite body, and the antistatic layer is preferably laminated on the surface of Layer A opposite to the surface on which Layer D is laminated.

[0075] <Method of manufacturing silicone composite> There are no particular limitations on the method for producing the silicone composite of the present invention, so long as it is a method that can laminate a base layer (A layer) on at least one side of the silicone molded article (D layer), and any known method can be used as the lamination method.

[0076] For example, a base layer (A layer) may be prepared and a silicone layer (D layer) may be prepared separately from this, and then these may be laminated together; a base layer (A layer) may be prepared and a silicone layer (D layer) may be prepared on this base layer (A layer) and then laminated together; conversely, a silicone layer (D layer) may be prepared and a base layer (A layer) may be prepared on this silicone layer (D layer) and then laminated together; or the base layer (A layer) and the silicone layer (D layer) may be prepared and then laminated together.

[0077] The process for producing the base layer (A layer) and the silicone layer (D layer) can be carried out by melt-kneading the raw material resins and extruding them with a single-screw or twin-screw extruder. The base layer (A layer) and the silicone layer (D layer) can be laminated by coextrusion, extrusion lamination, heat lamination, dry lamination, etc. Specifically, the base layer (A layer) and the silicone layer (D layer) may be simultaneously kneaded and coextruded by a feed block method or a multi-manifold method, etc., to be laminated together, or the base layer (A layer) and the silicone layer (D layer) may be prepared separately, and then the base layer (A layer) and the silicone layer (D layer) may be laminated together.

[0078] In the case of co-extrusion, the base layer (A layer) and the silicone layer (D layer) can be made into a laminate by using multiple extruders to merge the resins through a feed block or multi-manifold die.

[0079] In the case of extrusion lamination, the raw material for the silicone layer (D layer) is extruded from a T-die, I-die, etc. using a single-screw or twin-screw extruder, and then a single layer body that will become the silicone layer (D layer) is obtained using a roll method, tenter method, tubular method, etc. Next, when the raw material for the base layer (A layer) is extruded from a T-die, I-die, etc. using a single-screw or twin-screw extruder, it is laminated to the silicone layer (D layer) at the same time as casting, thereby obtaining the present composite.

[0080] In the case of thermal lamination and dry lamination, the raw material for the silicone layer (D layer) is extruded from a T-die, I-die, etc. using a single-screw or twin-screw extruder to obtain a monolayer body that will become the silicone layer (D layer). The base layer (A layer) is also produced using a similar method. Next, the base layer (A) and the silicone layer (D layer) are laminated under heating or by placing an adhesive layer between the layers, and the present composite can be obtained.

[0081] Among these, a preferred example of a method for producing a silicone composite, which is a method for producing a silicone composite consisting of a base layer (layer A), an undercoat layer (layer B), a thin film layer (layer C), and a silicone molded body (silicone layer) (layer D), will be described below.

[0082] First, a coating liquid as the undercoat layer (B layer) is applied to at least one side of the above-mentioned base layer (A layer), then dried, and further thermally crosslinked as necessary to form the undercoat layer (B layer). As the coating method, a known method suitable for the coating liquid can be applied, and the coating liquid may be applied to the base layer (A layer) stretched in a separate process, or the coating liquid may be directly applied to an unstretched sheet of the base layer (A layer) and then stretched to form the undercoat layer (B layer). In addition, in order to improve the leveling property and adhesion of the coating liquid, the coated surface of the base layer (A layer) may be previously subjected to a surface treatment such as a corona treatment.

[0083] Next, the thin film layer (C layer) is applied onto the undercoat layer (B layer). The coating method is not particularly limited as long as it is a method that can accurately obtain a thin film, as with the undercoat layer (B layer), but it is preferable to use a bar coater from the viewpoint of accuracy.

[0084] Furthermore, the silicone layer (D layer) is preferably laminated by the following method. First, an uncrosslinked silicone raw material is laminated on the thin film layer (C layer). As a lamination method, it is preferable to form an uncrosslinked silicone raw material (e.g., silicone elastomer resin) into a film or sheet shape by extrusion molding, injection molding, calendar molding, press molding, etc., and then laminate it on the thin film layer (C layer). Among them, it is more preferable to adopt the above-mentioned methods of extrusion lamination, heat lamination, dry lamination, etc., from the viewpoint of productivity. Alternatively, a method of forming a film directly on the thin film layer (C layer) by a known coating method may be used.

[0085] In the present invention, when a crosslinkable silicone raw material is used, it is preferable to subject the silicone raw material in an uncrosslinked state to a heat treatment. By subjecting the silicone raw material in an uncrosslinked state to a heat treatment, the low molecular weight cyclic siloxane contained in the silicone is volatilized, and the content of the low molecular weight cyclic siloxane in the obtained silicone composite tends to be reduced.

[0086] The stage of heat treatment of silicone raw material is not particularly limited. The silicone raw material may be heat-treated in advance and then a silicone layer (D layer) may be formed on the thin film layer (C layer), or the silicone raw material may be molded into a film or sheet shape and then heat-treated on an uncrosslinked silicone film or sheet, which is then laminated on the thin film layer (C layer), or the silicone layer (D layer) may be laminated on the thin film layer (C layer) to produce a silicone complex, and then heat-treated. Among these, it is preferable to heat-treat the uncrosslinked silicone raw material and then laminate it on the thin film layer (C layer) to form a complex, because of the large effect of reducing low molecular weight cyclic siloxane.

[0087] The heat treatment may be performed on the uncrosslinked silicone raw material as it is, but it is preferable to heat the plate-shaped molded product after molding it into a plate-shaped or other shape from the viewpoint of the effect of reducing low molecular weight cyclic siloxane. The thickness of the uncrosslinked plate-shaped or other molded product (before heat treatment) is preferably 10 mm or less, more preferably 6 mm or less, even more preferably 5 mm or less, particularly preferably 4 mm or less, and especially preferably 3.5 mm or less. With the above thickness, low molecular weight cyclic siloxane is volatilized, and the content of low molecular weight cyclic siloxane in the obtained silicone composite tends to be more easily reduced. In addition, from the viewpoint of handleability and processing amount, the lower limit is preferably 0.5 mm, more preferably 1 mm.

[0088] In the heat treatment, the heating temperature is preferably 100 to 280° C., more preferably 150 to 250° C., and even more preferably 160 to 230° C. By keeping the temperature within this range, the silicone is less likely to deteriorate, and the content of low-molecular-weight cyclic siloxane in the silicone composite tends to be further reduced.

[0089] In the heat treatment, the heating time is preferably 0.1 to 30 hours, more preferably 0.3 to 20 hours, further preferably 0.5 to 10 hours, particularly preferably 1 to 9 hours, and most preferably 1.5 to 8 hours. By keeping the heating time within the above range, the silicone is less likely to deteriorate, and the content of low-molecular-weight cyclic siloxane in the silicone composite tends to be effectively reduced.

[0090] Next, the silicone raw material in an uncrosslinked state is laminated and molded by the above method to produce a silicone composite, and the silicone is crosslinked and cured to obtain the silicone composite of the present invention. In the case where the silicone raw material is once molded into a plate-like shape or the like and heated in the heat treatment, it is preferable to plasticize the plate-like molded body after the heat treatment by a method such as roll kneading, trimix kneading, or planetary kneading, and then mold the silicone composite. Examples of means for crosslinking and curing the silicone include a method in which a curing catalyst, a curing agent, a crosslinking agent, or the like is added in advance to the silicone raw material used, and the silicone is cured by heat, light such as ultraviolet light, moisture in the air, or the like, and a method of crosslinking by irradiation with radiation.

[0091] In particular, the silicone layer (layer D) in the composite is preferably a radiation-cured product cured by irradiation with radiation. Curing by irradiation with radiation is preferred because there is no risk of loss of heat resistance or light resistance reliability due to residues of catalysts or crosslinking agents. In addition, it is preferred because sufficient adhesion is maintained between the thin film layer (layer C) and the silicone layer (layer D), thereby preventing problems such as delamination.

[0092] Examples of radiation include electron beams, X-rays, and gamma rays. These radiations are widely used industrially, can be easily used, and are energy-efficient. Among them, gamma rays are preferably used because they have almost no absorption loss and are highly transparent.

[0093] The dose of gamma rays can be appropriately selected and determined depending on the type of resin, the amount of crosslinking groups, and the type of radiation source. In the present composite, for example, the dose of gamma rays is preferably 20 to 150 kGy, more preferably 30 to 120 kGy, even more preferably 40 to 110 kGy, and particularly preferably 50 to 100 kGy. If the dose of exposure is equal to or greater than the lower limit, the silicone layer (D layer) can be sufficiently cured, and as a result, the desired compression set and durometer hardness tend to be easily obtained. On the other hand, if the dose of exposure is equal to or less than the upper limit, the increase in low molecular weight cyclic siloxane components due to decomposition reaction tends to be suppressed.

[0094] In addition, when selecting the irradiation dose, it is necessary to take into consideration the crosslink density of the silicone elastomer resin as well as the radiation resistance of the plastic film used as the base layer (layer A). In this regard, crystalline polyester resins are generally excellent in radiation resistance and are an example of a material for the base layer (layer A) that is highly suitable for the purpose of the present invention.

[0095] <Application> The silicone molded body (single layer) or silicone composite of the present invention has a reduced content of low molecular weight cyclic siloxane derived from silicone and is excellent in reducing thickness change, so that silicone, particularly silicone rubber, can be used in various applications by taking advantage of its properties (adequate adhesion and conformability to parts, etc.) For example, it can be used as a release material for various manufacturing processes, particularly press molding, vacuum molding, pressure molding, etc., a buffer material, an anti-slip material (sealing material), a carrier film or a protective film for transporting or protecting a workpiece, a fixing material for a liquid crystal display or a frame, an interlayer filler between a liquid crystal panel and a protective panel, a bonding material for a touch panel, etc. Among others, it can be suitably used as a release material, carrier film, or protective film in press molding such as hydraulic or hydraulic press molding, vacuum molding, or compressed air molding. For example, it can be suitably used as a release material, cushioning material, or anti-slip material in molding of display and touch panel related product components such as ICs, semiconductors, and passive components incorporated in electric and electronic products, and LED lighting product components. Among these, press molding is more suitable since it is less likely to deform even when used repeatedly. EXAMPLES

[0096] Examples will be described below, but the present invention is not limited to these examples.

[0097] <Example 1> 1. Heat treatment of silicone raw materials Millable silicone elastomer resin (KE-581-U, Type A durometer hardness 80, manufactured by Shin-Etsu Chemical Co., Ltd.) was kneaded in a roll mill (mixing roll mill, manufactured by Inoue Seisakusho Co., Ltd.) and pulled into a plate-like shape to produce a 3 mm-thick plate-shaped molded product of uncrosslinked silicone elastomer resin. The plate-shaped molded body was heated in an oven (temperature equipment research institute, thermo-cooling device ONDO) at 200°C for 5 hours (2.5 hours twice (front and back)), thereby volatilizing the low molecular weight cyclic siloxane and obtaining a silicone elastomer resin molded body of decyclic siloxane. Next, this silicone elastomer resin molding of decyclic siloxane was plasticized by being roll-kneaded again under the same conditions as above.

[0098] 2. Preparation of Silicone Composites A laminate of a substrate layer, an undercoat layer, a thin film layer, and an uncrosslinked silicone molded article (silicone layer) was prepared by the method described below, and crosslinked to obtain a silicone composite.

[0099] [Base material layer] As the substrate layer, a biaxially oriented polyethylene terephthalate (PET) film having a thickness of 100 μm (Diafoil T-100, specific gravity 1.4, manufactured by Mitsubishi Chemical Corporation) was prepared and subjected to a corona treatment.

[0100] [Undercoat layer] A coating solution was prepared by diluting 15 parts by mass of an amorphous polyester resin (Vylon 240, manufactured by Toyobo Co., Ltd.) and 2 parts by mass of a polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) with 85 parts by mass of a solvent (methyl ethyl ketone / toluene = 1 / 4 (mass ratio)). This was applied to the corona-treated surface of the base layer with a bar coater so that the thickness after drying would be 1.0 μm, and the coating solution was dried and crosslinked in an oven at 100°C for 10 minutes to form an undercoat layer.

[0101] [Thin film layer] A coating solution was obtained by diluting 20 parts by mass of a condensation type silicone resin composition (SRX290, manufactured by Toray Dow Corning Silicone Co., Ltd.) and 1.2 parts by mass of a curing agent (SRX242C, manufactured by Toray Dow Corning Silicone Co., Ltd.) with 78.8 parts by mass of a solvent (toluene). This was applied to the surface of the undercoat layer with a bar coater so that the thickness after drying would be 0.1 μm, and then dried and crosslinked in an oven at 100° C. for 10 minutes to form a thin film layer.

[0102] The above-mentioned heat-treated silicone raw material was supplied between the thin film layer of the laminate consisting of the substrate layer, undercoat layer and thin film layer, which was supplied along two calendars with a diameter of 100 mm, and a biaxially stretched PET film (Diafoil T-100, specific gravity 1.4, manufactured by Mitsubishi Chemical Corporation) used as a cover sheet, and a bank was formed on the roll at a roll temperature of 80°C to produce a composite of the substrate layer, undercoat layer and thin film layer laminate (100 μm) / silicone layer (300 μm) / cover sheet (100 μm). The obtained composite was irradiated with gamma rays to an absorbed dose of 50 kGy, and the silicone elastomer resin was crosslinked to obtain a composite (substrate layer (layer A) / undercoat layer (layer B) / thin film layer (layer C) / silicone layer (D) / cover sheet) in which the laminate consisting of the substrate layer, undercoat layer, and thin film layer was integrated with the silicone elastomer resin layer. The cover sheet was peeled off from this composite to obtain a silicone composite for evaluation consisting of substrate layer (layer A), undercoat layer (layer B), thin film layer (layer C), and silicone layer (D). The thickness of the obtained silicone composite was 410.9 μm.

[0103] <Example 2> A silicone composite was obtained in the same manner as in Example 1, except that in the heat treatment step of the silicone raw material, the thickness of the plate-shaped molded body used in the heat treatment was changed to 5 mm. The thickness of this silicone composite was 409.6 μm.

[0104] <Comparative Example 1> Except for not carrying out the heat treatment of the silicone raw material, a silicone composite was obtained in the same manner as in Example 1. The thickness of this silicone composite was 388.6 μm.

[0105] The physical properties in the examples and comparative examples were measured according to the following methods. The results are shown in Table 1.

[0106] (1) Content of low molecular weight cyclic siloxane As the internal standard solution, 5 mg of decamethylcyclopentasiloxane (cyclic siloxane pentamer (D5 siloxane)) was precisely weighed out and placed in a 100 mL measuring flask and made up to volume with acetone. 2 g of silicone composite was weighed out in a sample bottle, and 10 mL of the internal standard solution was weighed out. The sample bottle was covered with parafilm after being capped, and was immersed at a temperature of 23°C for 16 hours for extraction. The acetone solution in the sample bottle was then measured for low molecular weight cyclic siloxane content using gas chromatography (GC) under the following measurement conditions. The column temperature was held at 70°C for 1 minute, then increased to 320°C at a rate of 25°C / min, and held for 5 minutes before measurement.

[0107] (Measurement conditions) Measurement device: GC-2010Plus (Shimadzu Corporation) Column: Ultra ALLOY Capillary Column-UA1 (MS / HT) (100% dimethylpolysiloxane, length 30 m, inner diameter 0.25 mm, film thickness 0.1 μm) Carrier gas: Helium ·Flow rate: 1mL / min Detector: FID

[0108] (Calculation method for content) Using the amount of D5 siloxane as the internal standard and the GC peak area as the standard, each cyclic siloxane Dn was quantified from the peak area derived from each cyclic siloxane Dn (Dn is D4 to D20 siloxane, a cyclic siloxane having a dimethylsiloxane unit). For D5 siloxane, the amount of D5 siloxane as the internal standard was subtracted to perform quantification. In addition, since the measurements were performed on the silicone composite, the content of each cyclic siloxane in the silicone layer (Layer D: silicone molded product) was calculated using the thickness ratio of the base layer (Layer A) and the silicone layer (Layer D) of the composite and the specific gravity of each layer.

[0109] (2) Thickness change after pressing The silicone composite was pressed using a press machine (BIGHEART, manufactured by Imoto Seisakusho) at room temperature (23°C) with a pressure of 500 kg / cm. 2The thickness before pressing and the thickness after three pressings were measured under the above conditions, and the thickness change was calculated according to the following formula. The number of samples was two, and the average value of the two points was calculated as the thickness change value. [Formula]|T3-T0| T0: Thickness before pressing T3: Thickness after 3 pressings

[0110] (3) T 2H Included in silicone complex 1 H's T 2H ( 1 1 H spin-spin relaxation time was measured by the spin echo method using solid-state NMR under the following measurement conditions.

[0111] (Measurement conditions) ·Measuring device: Bruker AVANCEIII 400WB Probe: 4mmΦ CPMAS ·Measurement temperature: 23℃ Sample tube rotation speed: 5000Hz Observation core: 1 H(400.3MHz) Pulse sequence: Spin Echo · 1 H90° Pulse: 4.2μs×1.6dB(54W / 300W) Delay time τ: 1μs~100ms Pulse Delay: 20s -Capture time: 0.819s Accumulation count: 1 The relaxation behavior was calculated by curve fitting since it is expressed by the following formula.

number

[0112] (4) Tensile test Dumbbell-shaped No. 2 test pieces were prepared from each silicone composite, and tensile tests were performed in the machine direction of the film (longitudinal direction: MD direction) in accordance with JIS K6251:2017 using a tensile testing machine (Shimadzu Corporation, AGS-H, load cell capacity 1 kN) at a measurement temperature of 23°C, a gripping distance of 30 mm, and a stroke speed of 500 mm / min., and the elongation at break was measured.

[0113] [Table 1]

[0114] The silicone layer (silicone molded body) and silicone composite of the examples both contain a small amount of low molecular weight cyclic siloxane, which is a substance of high concern, and the change in thickness due to press molding is suppressed. 2H The time to hardness was short (hard) and the material had excellent durability. Therefore, for example, when used as a component of electric and electronic products, it is estimated that problems such as contact contamination, poor conduction, product contamination, etc. will be less likely to occur. In addition, even if it is used repeatedly as a cushioning material for press molding, it is estimated that the change in thickness is small, and the deterioration of the cushioning material's function can be suppressed.

[0115] In contrast, the silicone layer (silicone molded body) and silicone composite of the comparative example had a high content of low molecular weight cyclic siloxane and a relatively large change in thickness. 2H The time it took to dry was relatively long (soft) and it was less durable.

[0116] In addition, the pentamer (D5) of cyclic siloxane is particularly prone to volatilization or bleeding among low molecular weight cyclic siloxanes, and is a standard indicator for measuring the content of low molecular weight cyclic siloxanes, but in the examples, it was found that the content of the pentamer (D5) of cyclic siloxane was particularly suppressed. It is presumed that this suppresses the above-mentioned problems caused by the volatilization of low molecular weight cyclic siloxanes.

[0117] Furthermore, among low molecular weight cyclic siloxanes, those with a large number of cyclic siloxane subunits (D17-20 in an extreme example) are generally difficult to volatilize or bleed, and are thought to bleed with long-term or repeated use, but in the examples, it was found that the content of such cyclic siloxanes with a large number of subunits was also suppressed. This suggests that even with long-term or repeated use, the deterioration of function due to bleeding and contamination of molding machines, molded products, etc. can be suppressed.

[0118] Furthermore, since the silicone layer (silicone molded body) and silicone composite in the examples do not bleed low molecular weight cyclic siloxane and have little unnecessary stretching, they are considered to be useful as a release material for press molding and the like, a cushioning material, a carrier film used for pallets for transporting and storing electronic components such as semiconductors, flexible circuit boards, and microchips, and furthermore, as a protective film for robot arms, etc. [Industrial Applicability]

[0119] The silicone molded body or silicone composite of the present invention has a reduced content of low molecular weight cyclic siloxane derived from silicone and is excellent in reducing thickness change, and therefore can be used in various manufacturing processes, particularly as a release material, cushioning material, anti-slip material (sealing material) for press molding such as hydraulic or hydraulic press molding, vacuum molding, air pressure molding, etc., a carrier film such as a pallet for transporting and storing electronic parts, a protective film for a robot arm, etc., a fixing material for a liquid crystal display or frame, an interlayer filler between a liquid crystal panel and a protective panel, a bonding material for a touch panel, etc. Among them, it can be suitably used as a release material and cushioning material for press molding such as hydraulic or hydraulic press molding, vacuum molding, air pressure molding, etc. In particular, it can be suitably used as a release material, cushioning material, and anti-slip material when molding molded products such as display and touch panel related product components such as ICs, semiconductors, passive components, etc. incorporated in electric and electronic products, and LED lighting product components.

Claims

1. In a silicone molded article containing a cyclic siloxane, The silicone molded article has a content of 4-20 cyclic siloxane monomers of 7,400 ppm by mass or less, and is used for press molding, vacuum molding, or pressure molding.

2. 2. The silicone molded article according to claim 1, wherein the content of cyclic siloxane pentamer in the silicone molded article is 700 ppm by mass or less.

3. 3. The silicone molded article according to claim 1, wherein the content of cyclic siloxane heptamers to 20-mers in the silicone molded article is 6,400 ppm by mass or less.

4. 4. The silicone molded article according to claim 1, wherein the content of cyclic siloxane dimers to didecamers in the silicone molded article is 5,300 ppm by mass or less.

5. 5. The silicone molded article according to claim 1, wherein the content of cyclic siloxane 12-20 monomers in the silicone molded article is 4,600 ppm by mass or less.

6. 6. The silicone molded article according to claim 1, wherein the content of cyclic siloxane 15-20 monomers in the silicone molded article is 3,300 ppm by mass or less.

7. 7. The silicone molded article according to claim 1, wherein the content of cyclic siloxane 17-20 monomers in the silicone molded article is 2,100 ppm by mass or less.

8. The silicone molded article according to any one of claims 1 to 7, which contains a silicone elastomer resin.

9. 9. The silicone molded article according to claim 1, which is used as a mold release material, a cushioning material, or an anti-slip material in molding.

10. A silicone composite comprising the silicone molded article according to any one of claims 1 to 9 and a substrate layer laminated on at least one surface of the silicone molded article.

11. A silicone composite having a substrate layer on at least one surface of a silicone molded article containing a cyclic siloxane, the silicone composite having a content of 15-20 monomers of cyclic siloxane of 2,330 ppm by mass or less, and used for any one of press molding, vacuum molding, and pressure molding.

12. The silicone composite according to claim 11, wherein the content of cyclic siloxane 17-20 monomers in the silicone composite is 1,530 ppm by mass or less.

13. The silicone composite according to any one of claims 10 to 12, wherein the substrate layer contains a polyester resin.

14. The silicone composite according to any one of claims 10 to 13, wherein the silicone molded body contains a silicone elastomer resin.

15. The silicone composite according to any one of claims 10 to 14, which is used as a mold release material, a cushioning material, or an anti-slip material in molding.

16. A carrier film comprising the silicone molded article according to any one of claims 1 to 9 or the silicone composite according to any one of claims 10 to 15.

17. A protective film comprising the silicone molded article according to any one of claims 1 to 9 or the silicone composite according to any one of claims 10 to 15.

18. A method for producing a silicone molded product, comprising the steps of: forming uncrosslinked silicone into a plate-like molded product; subjecting the plate-like molded product to a heat treatment; plasticizing the plate-like molded product after heat treatment and then extruding it into a film or sheet; and subjecting the resulting film or sheet to a crosslinking treatment.

19. The method for producing a silicone molded article according to claim 18, wherein the plate-like molded article has a thickness of 10 mm or less.

20. The method for producing a silicone molded article according to claim 18 or 19, wherein the temperature in the heat treatment step is 100 to 280° C.

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