JP2020084014A - Silicone rubber molded body, blade rubber, method for producing silicone rubber molded body - Google Patents

Abstract

To provide a molded body that has sufficient flexibility and can suitably be used as a blade rubber in which the influence from bleeding liquid on wiping-surface is suppressed.SOLUTION: Provided is a silicone rubber molded body 1, made of a silicone rubber containing a platinum-based catalyst and having a crosslink structure and in which the crosslink structure is composed of a first crosslink structure derived from polyorganohydrogensiloxane and a second crosslink structure derived from a compound having 2 or more ethylenically unsaturated bonds in the molecule, and having a region with hardness distribution in which hardness gradually decreases from the surface toward the depth direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a silicone rubber molded body, a blade rubber, and a method for producing a silicone rubber molded body.

Conventionally, a blade rubber is provided in a wiper device for wiping a window of a vehicle. Some blade rubbers include a head portion, a lip portion that wipes a wiping surface such as glass, and a connecting portion that connects the head portion and the lip portion. The blade rubber is made of an elastic material such as natural rubber or synthetic rubber.

Further, conventionally, there is a silicone rubber molded body formed by curing a silicone rubber composition containing an organopolysiloxane and a curing agent.
For example, Patent Document 1 describes a method for molding a silicone rubber composition in which an organopolysiloxane that is a base polymer is mixed with wet silica, and then a curing agent is added to the mixture and a hot air vulcanization is performed at atmospheric pressure. Patent Document 1 describes a crosslinking reaction using an organic peroxide as a curing agent. Further, Patent Document 1 discloses that an organohydrogenpolysiloxane and a hydrosilylation catalyst are used in combination in a crosslinking reaction by an addition reaction.

Further, Patent Document 2 describes a method for producing a reflector in which a molded product obtained by solidifying a resin composition containing a silicone resin is irradiated with ionizing radiation.

JP, 2005-220263, A JP, 2017-2296, A

The blade rubber preferably has sufficient flexibility so that it can be deformed along the shape of the wiping surface. Further, the blade rubber is required to suppress the influence of the bleeding liquid on the wiping surface.
However, the conventional blade rubber has sufficient flexibility, and the influence of the bleed solution on the wiping surface has not been suppressed.

The present invention has been made in view of the above circumstances, and provides a molded body that has sufficient flexibility and can be suitably used as a blade rubber in which the influence of the bleeding liquid on the wiping surface is suppressed. The task is to do.
Another object of the present invention is to provide a blade rubber made of the above-mentioned molded product, having sufficient flexibility and suppressing the influence of the bleeding liquid on the wiping surface.
Another object of the present invention is to provide a method for producing the above-mentioned molded body that can be suitably used as a blade rubber.

The present inventor has earnestly studied to solve the above-mentioned problems, and has conceived the present invention. The present invention relates to the following items.
[1] Made of a silicone rubber having a crosslinked structure, containing a platinum-based catalyst,
The crosslinked structure is a first crosslinked structure derived from polyorganohydrogensiloxane,
A second cross-linked structure derived from a compound having two or more ethylenically unsaturated bonds in the molecule,
A silicone rubber molded article comprising a region having a hardness distribution in which the hardness gradually decreases from the surface in the depth direction.

[2] The compound having two or more ethylenically unsaturated bonds in the molecule is at least one of trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, and silicone diacrylate [1] The silicone rubber molded article according to.

[3] The silicone rubber molding according to [1] or [2],
A head part, a lip part for wiping the wiping surface, and a connecting part for connecting the head part and the lip part,
The blade rubber, wherein the lip portion has a hardness distribution in which the hardness gradually decreases from the surface toward the depth direction.

[4] The method for producing a silicone rubber molded article according to [1],
A composition preparation step of preparing a silicone rubber composition containing an uncured silicone rubber, a platinum-based catalyst, a polyorganohydrogensiloxane, and a compound having two or more ethylenically unsaturated bonds in the molecule;
And a curing step of curing the silicone rubber composition to form a molded article,
The curing step, a thermosetting step of heating the silicone rubber composition to form a thermoset;
A method for producing a silicone rubber molded article, which comprises a step of accelerating crosslinking by irradiating at least a part of the thermosetting product with radiation or ultraviolet rays.

[5] The method for producing a silicone rubber molded article according to [4], wherein the crosslinking promotion step is a step of irradiating the thermosetting product with an electron beam.
[6] In the crosslinking promoting step, the range of a region having a hardness distribution in which the hardness gradually decreases from the surface toward the depth direction is controlled by adjusting the acceleration voltage of the electron beam [ 4] or the method for producing a silicone rubber molded article according to [5].

The silicone rubber molded article of the present invention has sufficient flexibility and is provided with a region in which bleeding is suppressed, the region having a hardness distribution in which the hardness gradually decreases from the surface in the depth direction. .. Therefore, the blade rubber made of the silicone rubber molded article of the present invention, which uses the region in which bleeding is suppressed as the lip portion, has sufficient flexibility, and the influence of the bleeding liquid on the wiping surface was suppressed. Will be things.
According to the method for producing a silicone rubber molded article of the present invention, the silicone rubber molded article of the present invention which can be suitably used as a blade rubber can be produced.

It is a schematic sectional drawing which showed an example of a blade rubber. It is a graph which showed the relationship between the acceleration voltage and the penetration depth of an electron beam. 6 is a graph showing the relationship between the penetration depth of an electron beam and the energy arrival rate of the electron beam when the outermost surface is 100% at acceleration voltages of 50 keV, 70 keV, and 90 keV. 3 is a graph showing the relationship between the electron beam irradiation amount and the contact angle of non-water repellent glass in the thermosetting products of Example 1 and Comparative Example 1. 5 is a graph showing the relationship between the electron beam irradiation dose and the surface hardness of the thermosetting product of Example 1. 3 is a graph showing the relationship between the electron beam irradiation dose and the breaking strength of the thermosetting product of Example 1.

In order to solve the above problems, the present inventor has paid attention to a silicone rubber composition as a material for a blade rubber, and has conducted earnest studies as shown below.
As a result of studies by the inventors, it has been found that in a silicone rubber molding obtained by curing a silicone rubber composition, bleeding is less likely to occur as the surface hardness is higher. Therefore, as a method of suppressing the bleeding of the blade rubber made of the silicone rubber molded body, it is considered that the degree of crosslinking of the silicone rubber molded body is increased to increase the surface hardness. However, if the degree of cross-linking of the silicone rubber molding is increased, sufficient flexibility as a blade rubber cannot be obtained.

Therefore, in order to increase the surface hardness while ensuring the flexibility of the blade rubber made of the silicone rubber molded body, the present inventor forms a hardness distribution in which the hardness gradually decreases from the surface in the depth direction. We thought that it was good, and conducted repeated studies.
As a result, an uncured silicone rubber, a platinum catalyst as a crosslinking catalyst, a polyorganohydrogensiloxane as a crosslinking agent, and a compound having two or more ethylenically unsaturated bonds in the molecule as a crosslinking aid. It has been found that a thermoset product of a silicone rubber composition containing a can be formed and irradiated with radiation or ultraviolet rays to be crosslinked.

Further, the present inventor has found that among blade rubbers made of a silicone rubber molded body, at least the lip portion for wiping the wiping surface has a hardness distribution in which the hardness gradually decreases from the surface toward the depth direction. , It was thought that the influence of the bleed solution on the wiping surface could be suppressed. Then, it has been found that a silicone rubber molded body obtained by irradiating radiation or ultraviolet rays to at least a region of the thermosetting product of the silicone rubber composition, which will be the surface of the lip portion of the blade rubber, to be crosslinked, may be used.

In the silicone rubber molded body thus obtained, the first crosslinked structure derived from the crosslinking agent is formed substantially uniformly. In addition, a second crosslinked structure derived from a crosslinking aid is formed in the silicone rubber molded body. The number of the second cross-linked structures varies depending on the irradiation dose of radiation or ultraviolet rays, and increases as the irradiation dose of radiation or ultraviolet rays increases. Therefore, in the silicone rubber molded product manufactured by the above method, since the number of the second crosslinked structures gradually decreases from the surface to the depth direction, the hardness gradually increases from the surface to the depth direction. A region having a hardness distribution with a low value is formed.

In this silicone molded product, since the number of the second crosslinked structures in the deep portion from the surface (the surface of the region where there is no radiation or ultraviolet irradiation is also small) is small and the hardness is low, sufficient flexibility is obtained. can get. On the other hand, the surface of the region irradiated with the radiation or the ultraviolet ray has a high hardness because the number of the second cross-linking structures is large, and is a region in which bleeding is suppressed. Then, by using the region in which the bleed is suppressed as the lip portion of the blade rubber, it is possible to obtain the blade rubber having sufficient flexibility and suppressing the influence of the bleed liquid on the wiping surface.
The present inventor has completed the present invention based on such findings.

Hereinafter, the method for producing the silicone rubber molded body, the blade rubber, and the silicone rubber molded body of the present invention will be described in detail. The present invention is not limited to the embodiments described below.
In the present embodiment, as an example of the silicone rubber molded body of the present invention, a blade rubber made of the silicone rubber molded body of the present embodiment will be described as an example.

"Blade rubber (silicone rubber molding)"
FIG. 1 is a schematic sectional view showing an example of the blade rubber of the present embodiment. The blade rubber 1 shown in FIG. 1 is provided, for example, in a wiper device for wiping a window of a vehicle. The blade rubber 1 shown in FIG. 1 includes a head portion 10, a lip portion 11 that wipes the wiping surface, and a connecting portion 12 that connects the head portion 10 and the lip portion 11.

The lip portion 11 is connected to the connecting portion 12 via the connecting portion 12 and the neck portion 13 formed to have a width smaller in the short-side direction (wiping direction) than the lip portion 11. Due to the elastic deformation of the neck portion 13, the lip portion 11 is tiltable in the wiping direction with respect to the head portion 10 and the connecting portion 12.

The head portion 10 is provided with leaf spring insertion grooves 10a and 10a formed on both sides in the short-side direction so as to be recessed in the short-side direction (the reference numeral of one groove 10a is omitted). Each leaf spring insertion groove 10a is formed continuously in the longitudinal direction of the blade rubber 1. A leaf spring member 14 called a vertibra is inserted into each leaf spring insertion groove 10a.

The connecting portion 12 is formed to extend from the middle portion of the head portion 10 in the lateral direction toward the lip portion 11 side. As a result, the head portion 10 and the connecting portion 12 are substantially T-shaped in cross section.
In the connecting portion 12, a pair of arm portions 12a, 12a extending toward both sides in the lateral direction of the blade rubber 1 are formed at the end portion on the lip portion 11 side (the reference numeral of one arm portion 12a is omitted. ). On both sides of the connecting portion 12, a pair of holding grooves 12b, 12b, which are defined by the arm portion 12a and the head portion 10 and are formed to be recessed in the lateral direction, are provided (reference numeral of one groove 12b). Is omitted). Each holding groove 12b is formed continuously along the longitudinal direction of the blade rubber 1.

The blade rubber 1 is held by the blade holder 20. The blade holder 20 includes a top wall portion 20a, a pair of side wall portions 20b connected to both outer sides of the top wall portion 20a in the lateral direction, and a pair of holding claws 21 and 21 extending from one end portion of the side wall portion 20b. I have it.
The holding claws 21 and 21 of the blade holder 20 are inserted into the pair of holding grooves 12b and 12b of the blade rubber 1. As a result, the head portion 10 of the blade rubber 1 is sandwiched and held between the top wall portion 20a of the blade holder 20, the pair of side wall portions 20b and 20b, and the pair of holding claws 21 and 21.

The blade rubber 1 (silicone rubber molded body) of the present embodiment is made of a silicone rubber having a crosslinked structure, which contains a platinum-based catalyst described later.
The cross-linked structure of the blade rubber 1 of the present embodiment has a first cross-linked structure derived from a polyorganohydrogensiloxane described below and a second cross-linked structure derived from a compound having two or more ethylenically unsaturated bonds in the molecule described below. It consists of a cross-linked structure.

The blade rubber 1 of the present embodiment has a hardness distribution in which the hardness gradually decreases from the surface to the depth direction because the number of the second crosslinked structures gradually decreases from the surface to the depth direction. An area having is provided. In the blade rubber 1 shown in FIG. 1, at least the lip portion 11 is a region having a hardness distribution in which the hardness gradually decreases from the surface in the depth direction. In the blade rubber 1 of the present embodiment, the region having the hardness distribution in which the hardness gradually decreases from the surface in the depth direction may be the entire surface of the blade rubber 1.

The surface hardness of the lip portion 11 of the blade rubber 1 (silicone rubber molded body) of the present embodiment is, for example, preferably 80 degrees or higher, more preferably 82 degrees or higher, as measured by a type A durometer. preferable. The higher the surface hardness, the less bleeding is likely to occur, which is preferable. However, if the surface hardness of the lip portion 11 is too hard, the blade rubber 1 is less likely to fall to an appropriate wiping angle and the glass followability is deteriorated, and it becomes difficult to obtain good wiping performance. The measured hardness is preferably 93 degrees or less.
The breaking strength of the lip portion 11 of the blade rubber 1 (silicone rubber molded body) of this embodiment is preferably 7.5 MPa or more, and more preferably 8.0 MPa or more. When the breaking strength of the lip portion 11 is 7.5 MPa or more, the blade rubber 1 has good wear resistance.

"Method for manufacturing blade rubber 1 (silicone rubber molding)"
Next, as an example of a method for manufacturing the silicone rubber molded body of the present embodiment, a method for manufacturing a blade rubber made of the silicone rubber molded body of the present embodiment will be described as an example.
In order to manufacture the blade rubber 1 of this embodiment shown in FIG. 1, a composition preparation step of preparing a silicone rubber composition and a curing step of curing the silicone rubber composition to form a molded body are performed.

(Composition preparation process)
In the composition preparation step, a silicone rubber composition containing an uncured silicone rubber, a platinum catalyst, a polyorganohydrogensiloxane, and a compound having two or more ethylenically unsaturated bonds in its molecule is prepared.

[Uncured silicone rubber]
As the uncured silicone rubber used in this embodiment, for example, a millable silicone rubber can be used. The millable silicone rubber is similar to unvulcanized compound rubber such as natural rubber and ordinary synthetic rubber in a state before curing, and can be plasticized and mixed with a kneading roll machine or a closed mixer. It is a rubber compound. The millable silicone rubber contains polyorganosiloxane as a main raw material and further contains various additives for imparting various properties.

As the millable silicone rubber used in this embodiment, commercially available ones can be used. Specifically, KE-571-U, KE-1571-U, KE-951-U, KE-541-U, KE-551-U, KE-561-U, KE- manufactured by Shin-Etsu Chemical Co., Ltd. 961T-U, KE-1541-U, KE-1551-U, KE-941-U, KE-971T-U, etc. can be used.
These millable silicone rubbers may be used alone or in combination of two or more. Among these millable silicone rubbers, KE-571-U is preferably used because it has appropriate hardness and excellent workability.

[Platinum catalyst]
The platinum-based catalyst used in this embodiment is a crosslinking catalyst that promotes the addition reaction between the alkenyl group in the silicone rubber and the hydrosilyl group in the polyorganohydrogensiloxane.
Examples of the platinum-based catalyst include chloroplatinic acid, a complex obtained from chloroplatinic acid and an alcohol such as octyl alcohol, a platinum-ketone complex, a platinum-aldehyde complex, a platinum-olefin complex, and a platinum-vinylsiloxane complex. Platinum compounds; palladium complexes such as palladium-phosphine complexes; rhodium-phosphine complexes, rhodium complexes such as rhodium-sulfide complexes, and the like.

These platinum-based catalysts may be used alone or in combination of two or more. Among these platinum-based catalysts, in particular, they have excellent solubility in uncured silicone rubber and polyorganohydrogen siloxane and have good catalytic activity, and thus, a complex obtained from chloroplatinic acid and an alcohol, and/or platinum. -Preference is given to using vinylsiloxane complexes.
As the platinum-based catalyst used in this embodiment, a commercially available one can be used. Specifically, since it has good compatibility with KE-571-U, it is preferable to use C-25A manufactured by Shin-Etsu Chemical Co., Ltd.

[Polyorganohydrogen siloxane]
The polyorganohydrogensiloxane used in this embodiment is a cross-linking agent that forms a cross-linked structure by an addition reaction with an alkenyl group in the silicone rubber.
The polyorganohydrogensiloxane preferably has a viscosity at 25° C. of 10 to 100,000 mm ² /s, because it does not volatilize during storage and is easy to synthesize and handle. More preferably, it is 000 mm ² /s.
The siloxane skeleton of the polyorganohydrogensiloxane may be linear, branched, or cyclic, and it is preferable to use the linear one because it is easy to synthesize with good control.

The polyorganohydrogensiloxane may be used alone or in combination of two or more.
As the polyorganohydrogensiloxane used in this embodiment, commercially available products can be used. Specifically, since compatibility with KE-571-U is particularly good, it is preferable to use C-25B manufactured by Shin-Etsu Chemical Co., Ltd.

[Compound having two or more ethylenically unsaturated bonds in the molecule]
The compound having two or more ethylenically unsaturated bonds in the molecule used in the present embodiment is a crosslink having a plurality of ethylenically unsaturated bonds (-C=C-) which are radically polymerizable unsaturated bonds in the molecule. It is an auxiliary agent. Examples of the compound having two or more ethylenically unsaturated bonds in the molecule include a bifunctional compound shown below and/or a polyfunctional compound having three or more functional groups.
In the present embodiment, “(meth)acrylate” refers to one or more selected from “methacrylate” and “acrylate”.

Examples of the bifunctional compound include silicone di(meth)acrylate, di(meth)acrylate of 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, ethylene glycol di( (Meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, glycol di(meth)acrylate, neopentyl glycerin di(meth)acrylate, ethylene oxide adduct of bisphenol A di(meth)acrylate, propylene oxide adduct of bisphenol A di (Meth)acrylate, di(meth)acrylate of 2,2′-di(hydroxyethoxyphenyl)propane, di(meth)acrylate of tricyclodecane dimethylol, dicyclopentadiene di(meth)acrylate, pentane di(meth)acrylate 2,2-bis(glycidyloxyphenyl)propane di(meth)acrylic acid adduct and the like.

Examples of the polyfunctional compound include trimethylolpropane tri(meth)acrylate, trimethylolpropane trioxyethyl(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tris(acryloxy). Methyl) isocyanurate, tris(acryloxyethyl) isocyanurate, tris(acryloxypropyl) isocyanurate, triallyl trimellitic acid, triallyl isocyanurate and the like can be mentioned.

Only one kind of compound having two or more ethylenically unsaturated bonds in these molecules may be used, or two or more kinds thereof may be used.
The compound having two or more ethylenically unsaturated bonds in the molecule is an organic compound containing an amino group, a sulfur atom, a phosphorus atom, a nitrogen atom, an acetylene group, and a multiple bond so as not to hinder the crosslinking reaction of the silicone rubber. Those which do not contain a group or an organometallic base are preferred. As the compound having two or more ethylenically unsaturated bonds in such a molecule, any one or more selected from trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate and silicone diacrylate is used among the above compounds. Is more preferable.

[Other ingredients]
The silicone rubber composition contains an uncured silicone rubber, a platinum catalyst, a polyorganohydrogensiloxane, and a compound having two or more ethylenically unsaturated bonds in the molecule, and if necessary, other You may contain the component.
Other components include, for example, flame retardants, heat resistance improvers, thermal conductivity imparting agents, adhesiveness imparting agents, plasticizers, foaming agents, curing retardants, processing aids, and the like.

The silicone rubber composition contains, for example, an uncured silicone rubber, a platinum catalyst, a polyorganohydrogensiloxane, and a compound having two or more ethylenically unsaturated bonds in the molecule, if necessary. It can be prepared by mixing with other components.
As a method for mixing the raw materials to be the silicone rubber composition, for example, a kneader, a dough mixer, a Banbury mixer, a two-roll mill or the like can be used.

(Curing process)
In the curing step, the silicone rubber composition is cured to form a molded body (blade rubber 1). The curing step includes a thermosetting step of heating the silicone rubber composition to form a thermoset product, and a crosslinking promoting step of irradiating at least a part of the thermoset product with radiation or ultraviolet rays.

[Thermosetting step]
In the heat curing step, the silicone rubber composition is heated to form a heat cured product. The temperature and heating time for heating the silicone rubber composition in the heat curing step are appropriately selected depending on the shape and size of the blade rubber 1, the type of silicone rubber, the type and content of the platinum-based catalyst and polyorganohydrogensiloxane. I can decide.
The temperature for heating the silicone rubber composition can be, for example, 100 to 200°C. The time for heating the silicone rubber composition can be, for example, 10 to 20 minutes.

A known method can be used as a method for molding the silicone rubber composition, and the extrusion molding method is preferably used because the blade rubber 1 can be easily and continuously manufactured. More specifically, in the case of molding a silicone rubber composition using an extrusion molding method, a composition preparation step of preparing a silicone rubber composition, molding the silicone rubber composition using an extrusion molding method, and heating the composition. A thermosetting process for forming a thermoset product and a cross-linking promoting process for irradiating at least a part of the thermoset product with radiation or ultraviolet rays can be made into a line, and can be continuously and efficiently produced using a line production method.

[Cross-linking promotion step]
In the crosslinking promotion step, at least a part of the thermosetting product is irradiated with radiation or ultraviolet rays. In the present embodiment, radiation or ultraviolet rays are applied to at least the surface of the region of the blade rubber 1 that will be the lip portion 11. Radiation or ultraviolet rays may be applied to the entire thermoset.
When irradiating only a part of the thermosetting product with radiation or ultraviolet rays, it is preferable to mask the surface of the region not irradiated with radiation or ultraviolet rays with an aluminum foil or the like. When only the surface of the region of the blade rubber 1 that becomes the lip portion 11 is irradiated with radiation or ultraviolet rays, the portion not containing the second cross-linking structure and the portion having less second cross-linking structure in the blade rubber 1 are increased, resulting in more flexibility. An excellent blade rubber 1 (silicone rubber molded product) is obtained.

As the radiation, particle rays such as α rays, β rays, and electron rays may be used, or electromagnetic waves such as X rays may be used.
The crosslinking promotion step is preferably a step of irradiating the thermosetting product with an electron beam. Compared to other radiation, the electron beam can more easily control the depth that it reaches the thermosetting material. In addition, since the electron beam has higher energy than ultraviolet rays, radicals of the silicone rubber can be easily generated and crosslinking of the silicone rubber can be effectively promoted.

As shown below, generally, the penetration depth of an electron beam from the surface (material permeability) can be adjusted by the acceleration voltage.
The penetration depth of a general electron beam from the film surface can be measured by a CTA (cellulose triacetate) dosimeter. In the CTA dosimeter, the penetration depth of the electron beam is estimated using the characteristic that the absorbance increases linearly in proportion to the irradiated electron dose. FIGS. 2A to 2C show the relationship between the acceleration voltage and the penetration depth of the electron beam when the electron beam is irradiated using the accelerators having different energy ranges. By stacking CTA dosimeters with a thickness of 10 μm to 50 μm, it is possible to measure to what depth the electron beam has penetrated (reached) from the surface.

Using I-compact EB (registered trademark) (model: EC90/10/50L) manufactured by Iwasaki Electric Co., Ltd., a CTA dosimeter is irradiated with an electron beam with an accelerating voltage of 50 to 90 keV to determine the penetration depth of the electron beam. It was measured. The result is shown in FIG.
A CTA dosimeter is irradiated with an electron beam with an accelerating voltage of 80 to 250 keV using a standard EB experimental machine (model: EC250/30/180LS (LB2004)) manufactured by Iwasaki Electric Co., Ltd., and the penetration depth of the electron beam is measured. did. The result is shown in FIG.
The No. 1 accelerator (type: Cockcroft-Walton type) owned by Takasaki Quantum Applied Research Institute was used to irradiate the CTA dosimeter with an electron beam with an accelerating voltage of 500 to 2500 keV, and the penetration depth of the electron beam was measured. The result is shown in FIG.

As shown in FIGS. 2(A) to 2(C), the depth (penetration depth) at which the electron beam reaches the CTA dosimeter becomes deeper as the acceleration voltage increases. From this, it is expected that the depth (penetration depth) at which the electron beam reaches the thermosetting product of the silicone rubber composition of the present embodiment becomes deeper as the acceleration voltage increases.

Also, as a general theory, an electron beam causes an electromagnetic interaction with the electrons of the atoms forming the irradiation object when passing through the irradiation object to which the electron beam is irradiated, and gradually loses energy. (Ionization loss) Therefore, as shown below, the energy of the electron beam with which the irradiation target is irradiated can reach only a certain penetration depth determined according to the amount of energy irradiated. In addition, the amount of energy applied from the electron beam to the object to be irradiated becomes larger at a position closer to the surface of the object to be irradiated and becomes smaller at a position further away.

Using I-compact EB (registered trademark) (model: EC90/10/50L) manufactured by Iwasaki Electric Co., Ltd., CAT dosimeters are irradiated with electron beams with accelerating voltages of 50 keV, 70 keV, and 90 keV, respectively. The energy arrival rate of the electron beam in the depth direction was investigated. The result is shown in FIG. FIG. 3 is a graph showing the relationship between the penetration depth of the electron beam and the energy arrival rate of the electron beam when the outermost surface is 100% at acceleration voltages of 50 keV, 70 keV, and 90 keV.

As shown in FIG. 3, the depth reached by the electron beam (penetration depth) becomes deeper as the acceleration voltage increases. Further, as shown in FIG. 3, the amount of energy applied from the electron beam becomes larger at a position closer to the surface regardless of the magnitude of the acceleration voltage. From this, it is expected that the second crosslinked structure is formed at a higher density in a region closer to the surface in the region irradiated with the electron beam in the thermosetting product of the silicone rubber composition of the present embodiment.

In the crosslinking acceleration step, it is preferable to control the range of the region having the hardness distribution in which the hardness gradually decreases from the surface in the depth direction by adjusting the acceleration voltage of the electron beam.
Specifically, the acceleration voltage of the electron beam is preferably 40 keV to 2000 keV, more preferably 40 keV to 1000 keV, and further preferably 150 to 300 keV. The depth at which the electron beam reaches the thermosetting product becomes deeper as the acceleration voltage increases. By using an electron beam having an accelerating voltage of 2000 keV or less, preferably 300 keV or less, it is possible to suppress the reaction of silicone rubber having a deep depth from the surface in the thermosetting product. Therefore, the blade rubber 1 (silicone rubber molded body) having more excellent flexibility can be obtained. Further, by using an electron beam having an acceleration voltage of 300 keV or less, irradiation can be performed using a relatively inexpensive electron beam irradiation device. Further, by using an electron beam having an acceleration voltage of 40 keV or more, the effect of increasing the surface hardness by irradiating the electron beam becomes remarkable.

The irradiation dose of the electron beam is preferably 100 to 1000 kGy, and more preferably 200 to 500 kGy. When the irradiation amount of the electron beam is 100 kGy or more, the surface hardness becomes sufficiently high, and the bleeding suppressing effect by the irradiation of the electron beam becomes remarkable. Further, when the irradiation amount of the electron beam is 1000 kGy or less, it is possible to prevent the surface hardness from becoming too hard. Further, it is more preferable that the irradiation amount of the electron beam is 500 kGy or less, since the blade rubber 1 having good breaking strength can be obtained.
The irradiation amount of the electron beam can be appropriately determined according to the shape and size of the blade rubber 1, the type of silicone rubber, the type of compound having two or more ethylenically unsaturated bonds in the molecule, the content, and the like.

The blade rubber 1 (silicone rubber molded body) of the present embodiment is made of a silicone rubber having a crosslinked structure containing a platinum-based catalyst, and the crosslinked structure includes a first crosslinked structure derived from polyorganohydrogensiloxane and an intramolecular structure. And a second crosslinked structure derived from a compound having two or more ethylenically unsaturated bonds. In the blade rubber 1 of the present embodiment, the lip portion 11 is a region having a hardness distribution in which the hardness gradually decreases from the surface in the depth direction. Therefore, the blade rubber 1 of this embodiment has sufficient flexibility and has the lip portion 11 in which bleeding is suppressed.

On the other hand, for example, when the cross-linked structure does not have the second cross-linked structure but only the first cross-linked structure, if the first cross-linked structure is reduced in order to ensure sufficient flexibility, the bleeding of the lip portion may occur. It cannot be suppressed enough. When the crosslinked structure does not have the first crosslinked structure but only the second crosslinked structure, the hardness of the portion deep from the surface is insufficient, and sufficient hardness as a blade rubber cannot be obtained.

The method for producing the blade rubber 1 (silicone rubber molded body) of this embodiment has an uncured silicone rubber, a platinum catalyst, a polyorganohydrogensiloxane, and two or more ethylenically unsaturated bonds in the molecule. And a curing step of curing the silicone rubber composition to form a molded article, wherein the curing step heats the silicone rubber composition and heats it. It has a thermosetting step of forming a cured product and a crosslinking promoting step of irradiating at least a part of the thermoset product with radiation or ultraviolet rays. Therefore, according to the method for manufacturing the blade rubber 1 of the present embodiment, it is possible to manufacture a silicone rubber molded body that can be suitably used as the blade rubber 1.

More specifically, in the thermosetting step of the present embodiment, when the silicone rubber composition is heated, the alkenyl group in the silicone rubber and the hydrosilyl group in the polyorganohydrogensiloxane are added by being promoted by the platinum catalyst. react. As a result, the first crosslinked structure derived from polyorganohydrogensiloxane is formed in the thermosetting product substantially uniformly.
In the heat curing step of the present embodiment, since no radical is generated, the compound having two or more ethylenically unsaturated bonds in the molecule which is the crosslinking aid in the silicone rubber composition does not react. Therefore, the thermosetting product does not include the second crosslinked structure derived from the crosslinking aid.

Further, in the cross-linking promoting step of the present embodiment, when at least a part of the thermosetting product is irradiated with radiation or ultraviolet rays, radicals of the silicone rubber are generated, and two or more molecules in the molecule which is the crosslinking aid in the thermosetting product are generated. Reacts with compounds containing ethylenically unsaturated bonds. As a result, a second crosslinked structure derived from the crosslinking aid is formed in the blade rubber 1 after the crosslinking promotion step.

When the radiation or ultraviolet rays applied to the thermosetting material passes through the thermosetting material, it causes electromagnetic interaction with the electrons of the atoms that make up the thermosetting material, and gradually loses energy (ionization loss). To do. Therefore, the amount of energy applied by radiation or ultraviolet rays becomes larger as it is closer to the surface of the thermosetting product, and becomes smaller as it is farther away. Further, the radiation or the ultraviolet rays can reach only a certain penetration depth in the thermosetting material, which is determined according to the amount of energy applied.
The number of the second crosslinked structures increases as the irradiation amount (energy amount) of radiation or ultraviolet rays increases. Therefore, at least a part of the blade rubber 1 has the number of the second cross-linking structures gradually decreasing from the surface in the depth direction, so that the hardness gradually decreases from the surface to the depth direction. A region having a distribution is formed. That is, in the cross-linking promoting step of the present embodiment, by irradiating the thermosetting product with radiation or ultraviolet rays, it is possible to increase the surface hardness while suppressing an increase in the hardness of the deep portion from the surface.

On the other hand, for example, when the silicone rubber composition contains a peroxide as a cross-linking agent, heating the silicone rubber composition causes the peroxide not contained in the silicone rubber composition of the present embodiment. The crosslinked structure derived from the product is formed substantially uniformly. Furthermore, when the silicone rubber composition contains a peroxide, the crosslinking structure derived from the peroxide and the crosslinking structure derived from the compound having two or more ethylenically unsaturated bonds in the molecule are substantially uniform. Formed in. This is because the peroxide is thermally decomposed by heating the silicone rubber composition, hydrogen is extracted from the silicone rubber, and radicals of the silicone rubber are generated. The radical of the silicone rubber reacts with the compound having two or more ethylenically unsaturated bonds in the molecule to form a crosslinked structure derived from the compound having two or more ethylenically unsaturated bonds in the molecule.

Therefore, when the silicone rubber composition contains a peroxide as a crosslinking agent, the thermosetting material does not have a compound having two or more ethylenically unsaturated bonds in the molecule capable of reacting as a crosslinking assistant. .. Therefore, even if the thermosetting product of the silicone rubber composition is irradiated with radiation or ultraviolet rays, a cross-linked structure derived from a compound having two or more ethylenically unsaturated bonds in the molecule is not newly formed. Therefore, the cross-linked structure in the region irradiated with radiation or ultraviolet rays does not increase, and a region having a hardness distribution in which the hardness gradually decreases from the surface in the depth direction is not formed.

The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, a blade rubber made of a silicone rubber molded body has been described as an example of the silicone rubber molded body of the present invention. However, the silicone rubber molding of the present invention is not limited to blade rubber.
For example, the silicone rubber molding of the present invention can be applied to rolls for office machines such as copiers, multifunction machines, and printers. A roll for a copying machine, a roll for a multifunction machine, and a roll for a printer, which are made of the silicone rubber molded product of the present invention, have sufficient flexibility and suppress the bleeding liquid. As a result, a clear image free from color unevenness and color loss can be obtained by using a roll for a copying machine, a roll for a composite machine, or a roll for a printer, which is made of the silicone rubber molding of the present invention.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

"Example 1"
100 g of uncured silicone rubber (millable silicone rubber, Shin-Etsu Chemical Co., Ltd.; KE-571-U), 1 g of platinum-based catalyst (Shin-Etsu Chemical Co., Ltd.; C-25A), and polyorganohydrogensiloxane. (Shin-Etsu Chemical Co., Ltd.; C-25B) 4 g and a compound having 2 or more ethylenically unsaturated bonds in the molecule (trimethylolpropane trimethacrylate (TMPT)) 2 g are mixed using a double roll. By doing so, a silicone rubber composition was prepared.

The silicone rubber composition thus obtained was press-molded into a plate having a thickness of 2 mm and heated at 120° C. for 10 minutes to form a thermosetting product. The contact angle of the non-water repellent glass after pressure-bonding the thermosetting product was measured for the obtained thermosetting product by the method described below.

In addition, a plurality of thermosetting products of Example 1 were prepared, and an electron beam with an accelerating voltage of 90 keV was supplied from one surface using an electron beam irradiation device (eye compact EB, manufactured by Iwasaki Electric Co., Ltd.), 50 kGy, 100 kGy, 200 kGy, Irradiation was performed at each dose of 500 kGy and 1000 kGy to prepare a sample. For each sample, the contact angle of the non-water-repellent glass after pressing each sample so that the electron beam-irradiated surface contacts the non-water-repellent glass in the same manner as the thermosetting product not irradiated with the electron beam. Was measured. The result is shown in FIG.

"Measurement of contact angle of non-water repellent glass"
After wiping the surface of the thermosetting product with ethanol, it was left in a constant temperature bath at 60° C. for 30 minutes to cause bleeding. Then, a test piece having a length of 10 mm and a width of 40 mm was sampled from the thermosetting product in which bleeding was generated.
The test piece was placed on non-water-repellent glass (contact angle 30°), and a 2 kg roller was rolled back and forth twice from the top of the test piece for pressure bonding. Then, the test piece was peeled from the non-water repellent glass, and the contact angle of the portion of the non-water repellent glass that was in contact with the test piece was measured using a contact angle meter (MSA, manufactured by Cruz Co.). The contact angle was measured 3 seconds after supplying 1 μl of water to the measurement surface.

"Comparative Example 1"
100 g of uncured silicone rubber (millable silicone rubber, Shin-Etsu Chemical Co., Ltd.; KE-571-U), 1 g of platinum-based catalyst (Shin-Etsu Chemical Co., Ltd.; C-25A), and polyorganohydrogensiloxane. (Shin-Etsu Chemical Co., Ltd.; C-25B) 4g was mixed using a two-roll to prepare a silicone rubber composition.

The silicone rubber composition thus obtained was press-molded into a plate having a thickness of 2 mm and heated at 120° C. for 10 minutes to form a thermosetting product. Regarding the obtained thermosetting product, the contact angle of the non-water repellent glass after pressure-bonding the thermosetting product was measured in the same manner as in Example 1.

In addition, a plurality of thermosetting products of Comparative Example 1 were prepared, and an electron beam with an accelerating voltage of 90 keV was irradiated from one surface with an electron beam irradiation device (Eye Compact EB, manufactured by Iwasaki Electric Co., Ltd.) to 50 kGy, 100 kGy, 200 kGy, Irradiation was performed at each dose of 500 kGy and 1000 kGy to prepare a sample. Then, with respect to each sample, the contact angle of the non-water repellent glass after the pressure bonding of each sample was measured in the same manner as the thermosetting product not irradiated with the electron beam. The result is shown in FIG.

FIG. 4 is a graph showing the relationship between the electron beam irradiation amount and the contact angle of the non-water repellent glass in the thermosetting products of Example 1 and Comparative Example 1. As shown in FIG. 4, in Example 1 in which the silicone rubber composition containing TMPT, which is a crosslinking aid, was used, as compared with Comparative Example 1 in which the silicone rubber composition containing no TMPT was used, the non-water repellent glass was used. Contact angle was reduced. Particularly, when the electron beam irradiation amount was 200 to 1000 kGy, the contact angle of the non-water repellent glass was small.
This result is presumed to be because in Example 1, irradiation with an electron beam formed a crosslinked structure derived from TMPT to suppress bleeding.

Similarly to the sample in which the contact angle of the non-water repellent glass was measured, the sample was made of the thermosetting material of Example 1 and was irradiated with an electron beam having an acceleration voltage of 2 MeV at respective irradiation doses of 50 kGy, 100 kGy, 200 kGy, 500 kGy, and 1000 kGy. A sample was prepared and the surface hardness was measured by the method described below. The result is shown in FIG.
(Measuring method of surface hardness)
The surface hardness of each sample was measured using a type A durometer hardness meter (Asker rubber hardness meter DD2, manufactured by Kobunshi Keiki Co., Ltd.).

FIG. 5 is a graph showing the relationship between the electron beam irradiation amount and the surface hardness of the thermosetting product of Example 1. As shown in FIG. 5, it was confirmed that the surface hardness of the thermosetting product increased as the electron beam irradiation amount increased. In particular, it has been found that when the electron beam irradiation amount is 100 kGy or more, good surface hardness is obtained. It is presumed that this result is due to the formation of a crosslinked structure derived from TMPT by irradiation with an electron beam.

Similarly to the sample in which the contact angle of the non-water repellent glass was measured, the sample was made of the thermosetting material of Example 1 and was irradiated with an electron beam having an acceleration voltage of 2 MeV at respective irradiation doses of 50 kGy, 100 kGy, 200 kGy, 500 kGy, and 1000 kGy. A sample was prepared and the breaking strength was measured by the method described below. The result is shown in FIG.
(Measurement method of breaking strength)
A JIS K6251 No. 3 dumbbell-shaped tensile test piece was sampled from each sample, and a tensile test was performed at a tensile speed of 500 mm/min to measure the breaking strength.

FIG. 6 is a graph showing the relationship between the electron beam irradiation amount and the breaking strength in the thermosetting product of Example 1. As shown in FIG. 6, it was found that the breaking strength tends to decrease as the irradiation amount of the electron beam increases. Further, it is understood that the irradiation dose of the electron beam is preferably 500 kGy or less in order to obtain a good breaking strength as the blade rubber.

"Example 2"
A silicone rubber composition was prepared in the same manner as in Example 1 except that ethylene glycol dimethacrylate was used as the compound having two or more ethylenically unsaturated bonds in the molecule, and a thermoset product thereof was formed.

"Example 3"
A silicone rubber composition was prepared in the same manner as in Example 1 except that silicone diacrylate was used as the compound having two or more ethylenically unsaturated bonds in the molecule, and a thermoset product thereof was formed.

"Example 4"
A silicone rubber composition was prepared in the same manner as in Example 1 except that KE-941-U manufactured by Shin-Etsu Chemical Co., Ltd., which was a millable silicone rubber, was used as the uncured silicone rubber, and the thermosetting thereof was performed. Formed.

An electron beam with an accelerating voltage of 90 keV is irradiated from 200 kGy from one surface of the thermosetting products of Examples 2 to 4 thus obtained using an electron beam irradiation device (eye compact EB, manufactured by Iwasaki Electric Co., Ltd.). Irradiated in dose. Then, in the same manner as in the thermosetting product of Example 1, the contact angle of the non-water repellent glass after the thermosetting product irradiated with the electron beam of 200 kGy was pressure bonded was measured. The results are shown in Table 1.

In addition, Table 1 also shows the result of the contact angle of the non-water repellent glass after the thermosetting material of Example 1 irradiated with the electron beam of 200 kGy was pressure bonded.

"Comparative example 2"
A silicone rubber composition was prepared in the same manner as in Example 1 except that a compound having two or more ethylenically unsaturated bonds in the molecule was not included, and a thermoset product thereof was formed. Regarding the obtained thermosetting product, the contact angle of the non-water repellent glass after pressure-bonding the thermosetting product was measured in the same manner as in Example 1. The results are shown in Table 1.

"Comparative Example 3"
A silicone rubber composition was prepared in the same manner as in Example 4 except that a compound having two or more ethylenically unsaturated bonds in the molecule was not included, and a thermoset product thereof was formed. Regarding the obtained thermosetting product, the contact angle of the non-water repellent glass after pressure-bonding the thermosetting product was measured in the same manner as in Example 1. The results are shown in Table 1.

As shown in Table 1, the contact angle of the non-water-repellent glass after press-bonding the thermosetting products irradiated with the electron beam of 200 kGy of Examples 1 to 3 has two or more ethylenically unsaturated bonds in the molecule. It was smaller than the contact angle of the non-water-repellent glass after pressure bonding the thermosetting product of Comparative Example 2 containing no compound having it.
As shown in Table 1, the contact angle of the non-water repellent glass after the thermosetting product irradiated with the electron beam of 200 kGy of Example 4 was pressure-bonded was a compound having two or more ethylenically unsaturated bonds in the molecule. It was smaller than the contact angle of the non-water repellent glass after pressure bonding of the thermosetting product of Comparative Example 3 not containing.

From the results shown in Table 1, in Examples 1 to 4, by irradiation with an electron beam, a crosslinked structure derived from a compound having two or more ethylenically unsaturated bonds in the molecule was formed, and bleeding was suppressed. It is estimated that

1 Blade rubber (silicone rubber molding)
10 head part 11 lip part 12 connecting part 13 neck part 14 leaf spring member 20 blade holder

Claims (6)

It contains a platinum-based catalyst and is made of silicone rubber with a cross-linked structure.
The crosslinked structure is a first crosslinked structure derived from polyorganohydrogensiloxane,
A second cross-linked structure derived from a compound having two or more ethylenically unsaturated bonds in the molecule,
A silicone rubber molded article comprising a region having a hardness distribution in which the hardness gradually decreases from the surface in the depth direction. The compound having two or more ethylenically unsaturated bonds in the molecule is at least one of trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, and silicone diacrylate. Silicone rubber molding. The silicone rubber molded body according to claim 1 or 2,
A head part, a lip part for wiping the wiping surface, and a connecting part for connecting the head part and the lip part,
A blade rubber, wherein the lip portion is a region having a hardness distribution in which the hardness gradually decreases from the surface in the depth direction. A method for producing a silicone rubber molded body according to claim 1, wherein
A composition preparation step of preparing a silicone rubber composition containing an uncured silicone rubber, a platinum-based catalyst, a polyorganohydrogensiloxane, and a compound having two or more ethylenically unsaturated bonds in the molecule;
And a curing step of curing the silicone rubber composition to form a molded article,
The curing step, a thermosetting step of heating the silicone rubber composition to form a thermoset;
A method for producing a silicone rubber molded article, which comprises a step of accelerating crosslinking by irradiating at least a part of the thermosetting product with radiation or ultraviolet rays. The method for producing a silicone rubber molded article according to claim 4, wherein the crosslinking promotion step is a step of irradiating the thermosetting product with an electron beam. In the cross-linking promoting step, the range of a region having a hardness distribution in which the hardness gradually decreases from the surface in the depth direction is controlled by adjusting the accelerating voltage of the electron beam. The method for producing the silicone rubber molded body according to claim 5.

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