JP5189015B2 - Rubber sheet for laminate and laminate - Google Patents

Description

  The present invention relates to a laminated rubber sheet and a laminated body of the laminated rubber sheet and a prepreg, and particularly useful for laminated bodies useful as sealing materials for electrolytic capacitors, sealing materials for precision products that enclose liquids and gases, and the like. The present invention relates to a rubber sheet and a laminate.

An electrolytic capacitor is usually a case, a capacitor element housed in the case, an electrolyte impregnated in the capacitor element, and a sealing material that seals the opening of the case and prevents evaporation of the electrolyte. And leads that are drawn from the capacitor element and penetrate the sealing material. As this sealing material, a laminate in which an appropriate number of prepregs obtained by impregnating a paper base with a phenolic resin and a vulcanized rubber sheet such as styrene-butadiene rubber and ethylene-propylene-terpolymer has been conventionally used. Yes. The encapsulant laminate requires that the prepreg and the rubber sheet are firmly bonded and integrated, have heat resistance, and have a small deterioration in characteristics even at high temperatures.
As a laminate for such a sealing material, a laminate of a rubber sheet containing 1 to 50 parts by weight of a polyhydric alcohol with respect to 100 parts by weight of rubber and a resin-containing sheet containing a synthetic resin is known. (Patent Document 1).

Also, as a rubber-laminated laminate, an organic peroxidation with a 1 minute half-life of 130 ° C. to 160 ° C. with respect to 100 parts by weight of an ethylene-propylene-nonconjugated diene rubber having Mooney viscosity (ML _{1 + 4} 100 ° C.) of 60 to 110 objects 1-8 parts by weight Mooney viscosity consisting of those containing silicate hydrate 10-80 parts by weight _{(ML 1 + 4 100 ℃)} 85~160, and Curelastometer vulcanization rate index (t _{△ 80} 130 ℃) 15 A rubber-laminated laminate is known in which a workpiece is formed by overlapping an unvulcanized rubber sheet and a phenol resin-impregnated prepreg of ˜30 minutes, and the workpiece is heated and pressed to be integrally molded. Here, the Mooney viscosity and the curastometer vulcanization rate index are defined in the unvulcanized rubber physical test method (JISK6300-1 and JISK6300-2). The Mooney viscosity (ML _{1 + 4} 100 ° C.) indicates the Mooney viscosity after rotating the rotor at 100 ° C. using a large rotor for 1 minute, and further for 4 minutes. Curast meter vulcanization rate index (t _{△ 80} 130 ° C) is the difference between 10% ME and 90% ME as the difference ME between minimum value ML and maximum value MH of vulcanization at 130 ° C. t _{c (10)} and t _{c (90)} are taken and further represented by t _{c (90)} −t _{c (10)} = t _{c (Δ80)} (Patent Document 2).

On the other hand, the sheet thickness of the sheet-like polymer composition used for various waterproof sheets such as waterproof sheets for construction, civil engineering and truck tarpaulins is less than the sheet thickness. A sheet having both an electron beam crosslinked layer and an uncrosslinked layer obtained by irradiating an electron beam from one side under an acceleration voltage of 30 to 70% is disclosed (Patent Document 3).
However, since the sealing material for electrolytic capacitors described in Patent Document 1 contains a polyhydric alcohol in the rubber sheet, the polyhydric alcohol is a rubber depending on the elapsed time from the production of the rubber sheet to the lamination with the resin-containing sheet. It may ooze out on the surface of the sheet and may not have a desired adhesive force or become unstable when laminated with a resin-containing sheet. Moreover, since the only factor contributing to adhesion to the resin-containing sheet is polyhydric alcohol, it is difficult to obtain a strong adhesive force. When an unvulcanized rubber sheet is used for bonding to the resin-containing sheet, the unvulcanized rubber and the uncured resin are caused by a mutual chemical reaction between the rubber vulcanization reaction and the resin-containing sheet curing reaction. A strong adhesive force can be obtained by a physical reaction due to the anchoring effect with the containing sheet, but there is a problem in that it is difficult to obtain a product having a desired dimensional accuracy due to a large change in rubber dimensions due to heating and pressurization performed at the time of lamination. .
The rubber-laminated laminate described in Patent Document 2 has a problem that it is difficult to perform kneading, sheeting, or the like in order to handle a high viscosity material.
The sheet described in Patent Document 3 has a problem that adhesive strength is poor when it is laminated with a prepreg.

Japanese Patent Laid-Open No. 5-140343 Japanese Patent No. 3993785 JP-A-5-295136

  The present invention has been made to cope with such problems, and has a rubber sheet for a laminate having excellent adhesive strength, excellent dimensional stability, excellent productivity, and excellent sealing properties. It aims at providing the laminated body of this rubber sheet for laminated bodies, and a prepreg.

The rubber sheet for a laminate of the present invention is a rubber sheet for a laminate laminated on a prepreg, and the rubber sheet has a Mooney viscosity (ML _{1 + 4} 125 ° C.) at the time of non-crosslinking of 50 to 100, non adhesive surface is crosslinked by at least an electron beam irradiation from the non-adhesive surface on the opposite side of the adhesive surface in contact with the prepreg, characterized in that the adhesive surface is uncrosslinked.
The rubber sheet is characterized in that a compound having a plurality of polymerizable unsaturated double bonds in the molecule is blended.
In particular, the compound having a plurality of polymerizable unsaturated double bonds in the molecule is a (meth) acrylic acid ester of a polyhydric alcohol. Here, (meth) acrylic acid ester represents acrylic acid ester and / or methacrylic acid ester.
The laminate of the present invention is a laminate of a prepreg and the above rubber sheet for laminate.

The rubber sheet for a laminate of the present invention contains a compound having a plurality of polymerizable unsaturated double bonds in the molecule, particularly a (meth) acrylic acid ester of a polyhydric alcohol, and has a Mooney viscosity (ML ₁₎ at the time of uncrosslinking. ₊₄ 125 ° C.) is 50 to 100, and the non-adhesive surface side opposite to the adhesive surface in contact with the prepreg is cross-linked by at least electron beam irradiation, so that it is due to the polymerizable unsaturated double bond remaining on the adhesive surface. When the cross-linking occurs, the prepreg is firmly adhered to each other, and the Mooney viscosity of the rubber at the time of non-cross-linking is adjusted, whereby a laminate having excellent dimensional stability can be formed. Since the laminate obtained in this way is excellent in heat resistance and sealing properties, it can be used for packing for electrolytic capacitors and the like.

  As the rubber that can be used in the present invention, a rubber that can be crosslinked by electron beam irradiation can be used. Examples thereof include butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene-propylene rubber, ethylene-propylene-nonconjugated diene rubber, acrylic rubber, silicone rubber, and fluorine rubber. Among these, ethylene-propylene rubbers such as ethylene-propylene rubber and ethylene-propylene-nonconjugated diene rubber which are inexpensive and excellent in heat resistance are preferable. The rubber can be used alone or as a mixed rubber.

  The rubber contains a compound having a plurality of polymerizable unsaturated double bonds in the molecule. It is preferable to have 2 or more, particularly 3 or more polymerizable unsaturated double bonds. Examples of such compounds include polyhydric alcohol acrylic acid esters and methacrylic acid esters, polyhydric carboxylic acid allyl esters, triallyl isocyanurate, triallyl cyanurate, and the like. Among these, a (meth) acrylic acid ester of a polyhydric alcohol is preferable because it improves adhesiveness. Examples of the (meth) acrylic acid ester of polyhydric alcohol include trimethylolpropane triarylate and trimethylolpropane trimethacrylate. Any one of these compounds may be used alone, or two or more thereof may be used in combination.

  The crosslinking agent that can be blended with the rubber is preferably an organic peroxide, such as benzoyl peroxide, lauroyl peroxide, monochlorobenzoyl peroxide, 2,4 dichlorobenzoyl peroxide, t-butylcumyl peroxide, 2,5- Dimethyl-2,5bis (t-butylperoxy) hexane, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-bis-t-butylperoxy-3, 3,5-trimethylcyclohexane, di-t-butyl peroxide, t-butylcumyl peroxide and the like can be exemplified.

Other rubber additives can be blended with the rubber that can be used in the present invention. Examples thereof include a vulcanization aid, a vulcanization accelerator, a vulcanization retarder, an anti-aging agent, a reinforcing agent or a filler, a processing aid or a lubricant, and a colorant.
Metal oxides as vulcanization aids, antioxidants and UV absorbers as anti-aging agents, carbon black, anhydrous silicic acid, calcium silicate, aluminum silicate as reinforcing agent or filler, Clay, calcium carbonate, talc, barium sulfate, alumina sulfate, lithopone, styrene resin, phenol resin, petroleum resin, recycled rubber, etc., and processing aids or lubricants include stearic acid, metal stearate soap, waxes, etc. It is done.

The proportion of each component in the rubber layer that can be cross-linked by electron beam irradiation is 0.5 to 20 parts by weight of a compound having a plurality of polymerizable unsaturated double bonds in the molecule, preferably 100 parts by weight of the raw rubber. 1 to 10 parts by weight can be blended. If the amount is less than 0.5 parts by weight, the adhesiveness is insufficient, and if it exceeds 20 parts by weight, the adhesiveness reaches a saturated state and further effects cannot be obtained, and blooming is likely to occur.
Moreover, 1-20 weight part of organic peroxides, Preferably 1-10 weight part can be mix | blended.
When the ratio of the organic peroxide exceeds 20 parts by weight, curing occurs and it is not suitable for practical use. If the amount is less than 1 part by weight, crosslinking is not sufficient.
The rubber that can be used in the present invention may further contain 20 to 250 parts by weight, preferably 30 to 150 parts by weight of a reinforcing agent and a filler with respect to 100 parts by weight of the raw rubber. If the reinforcing agent and the filler exceed 250 parts by weight, the raw rubber fabric becomes hard and the sheeting process becomes difficult. On the other hand, when the amount is less than 20 parts by weight, the reinforcing effect of the rubber is so low that required characteristics cannot be obtained.

The rubber composition that can be used in the present invention has a Mooney viscosity (ML _{1 + 4} 125 ° C.) at the time of non-crosslinking of 50 to 100, preferably 60 to 90. When the Mooney viscosity is within this range, sheeting processing stability and dimensional stability when laminated with a prepreg can be maintained. That is, the surface dimensional change rate of the rubber described later can be 25% or less. If the Mooney viscosity is less than 50, the surface dimensional change rate of the rubber increases, and if it exceeds 100, the sheeting processability becomes difficult.
Mooney viscosity can be measured by the method of JIS K 6300-1.

The method of compounding the rubber with the compounding agent is not particularly limited, and for example, when a rubber compound is produced, it can be performed using a rubber kneader such as a two-roll, Banbury mixer, internal mixer, kneader or the like.
Moreover, the thickness of a rubber sheet can be set suitably according to a use. When used as a capacitor packing, it is usually preferably about 0.1 to 5 mm.

  The electron beam irradiation conditions for the rubber layer are an acceleration voltage of 100 to 3000 kV, preferably 150 to 750 kV, an irradiation dose of 10 to 1000 kGy, preferably more than 10 kGy and 600 kGy or less. When the acceleration voltage is less than 100 kV, the thickness of the cross-linked layer is thin, and when the irradiation dose is less than 10 kGy, the cross-link density is reduced and the dimensional change of the rubber is increased. When the acceleration voltage exceeds 3000 kV, the thickness of the cross-linked layer becomes thick, and when the irradiation dose exceeds 1000 kGy, the cross-linking density becomes too high, so that the adhesive force with the prepreg is reduced.

The method of irradiating the rubber sheet with the electron beam from the non-adhesive surface side of the prepreg, the method of performing from the adhesive surface side of the prepreg, and the method of performing from both the non-adhesive surface side and the adhesive surface side of the prepreg can be adopted.
Among these electron beam irradiations, a preferable method is a method performed from the non-adhesive surface side. By irradiating from the non-adhesive surface side, the non-adhesive surface side can be cross-linked and the adhesive surface side can be uncross-linked.
Moreover, when irradiating an electron beam also from the adhesion surface side, it is preferable that an irradiation dose shall be 10 kGy or less. If it exceeds 10 kGy, the crosslink density increases and the adhesive strength with the prepreg decreases.
By adjusting the accelerating voltage and irradiation dose, which are electron beam irradiation conditions, according to the thickness, density, and the like of the rubber sheet, a rubber sheet as a gradient material with a high crosslinking density on the non-adhesive surface side can be obtained.

The rubber sheet for laminates of the present invention can be evaluated by the following method.
(1) Adhesiveness The adhesion state of the interface between the rubber sheet and prepreg of the laminate is confirmed. If the crosslink density on the adhesive surface side of the rubber sheet becomes too high, the adhesive strength between the rubber sheet and the prepreg is inferior, and peeling occurs at the interface between the rubber sheet and the prepreg. When the crosslink density on the adhesive surface side of the rubber sheet is in an appropriate range, the rubber sheet layer is destroyed even if an attempt is made to separate the rubber sheet and the prepreg.
For example, using a resol-type phenol resin-impregnated paper as a prepreg, laminating and bonding is performed under the conditions of a pressing surface pressure of 100 kg / cm ² , a temperature of 170 ° C., and a pressing time of 1 hour (a rubber layer of a rubber layer). A thickness of 1 mm and a resin layer thickness of 1.5 mm) were obtained. This laminate is cut to a width of 25 mm, the end of the laminate is turned, a 180 degree peel test is performed at the interface according to JISK6256, and the fracture condition of the adhesive surface when the length is peeled 150 mm is observed. When the rubber sheet breaks or breaks, the rubber breaking rate is 90% or more. In this case, the crosslink density of the adhesive surface of the rubber sheet is in an appropriate range.
(2) Dimensional change at the time of laminating and bonding When the non-adhesive surface side of the laminate produced under the above conditions is not sufficiently cross-linked, the dimensional change of the rubber sheet after heat-pressure bonding between the rubber sheet and the prepreg becomes large. When measured using a square rubber sheet size, if the rate of change in the surface dimensions of the rubber sheet after lamination is 25% or less, preferably 20% or less with respect to the rubber sheet size before lamination, Adhesive surface crosslink density and rubber Mooney viscosity are appropriate.
The area dimensional change rate is expressed by the following equation.

Area dimensional change rate (%) = ((L ₂ −L ₁ ) / L ₁ ) × 100

Here, L ₁ is the length of one side of the square rubber sheet before lamination adhesion, and L ₂ is the average length of one side of the square rubber sheet after lamination adhesion.

The laminated rubber sheet of the present invention can be used for producing a sealing material for electrolytic capacitors and precision products for enclosing liquids and gases by laminating with a prepreg. The laminate can be used for nickel-hydrogen battery packing, capacitor packing, and the like.
Since the adhesive sheet side of the rubber sheet for laminate of the present invention is in an uncrosslinked or semi-crosslinked state, crosslinking and adhesion reaction of the rubber sheet occur at the same time when the prepreg is laminated and bonded. Furthermore, since the non-adhesive surface side is cross-linked, the dimensional change of the rubber sheet is small and the dimensional stability is excellent. For this reason, the laminated body with a prepreg has a high degree of sealing performance, and since this excellent sealing performance does not deteriorate for a long time, the reliability of capacitors and precision products can be improved and the size can be reduced.

  In the present invention, the prepreg refers to a sheet of an uncured resin alone or a sheet obtained by impregnating a base material with an uncured resin. As the substrate, for example, paper, glass cloth, glass nonwoven fabric, polyester sheet, polyester nonwoven fabric, aromatic polyamide paper (DuPont's trade name, Nomex), or a combination thereof can be used. As the uncured resin, an uncured thermosetting resin is preferable, and examples thereof include an epoxy resin, a phenol resin, a polyimide resin, an imide-modified epoxy resin, an aralkyl ether resin, a polyvinyl phenol resin, and a bismaleimide / triazine resin. it can. In particular, epoxy resins and resol type phenol resins are preferred.

  The thickness of the prepreg to be laminated and bonded is preferably 0.05 to 5.0 mm. As a specific example, a resol type phenol resin-impregnated paper having a thickness of about 0.2 to 0.4 mm can be suitably used. A plurality of prepregs having such a thickness can be used in piles.

  Lamination of the prepreg and the laminated rubber sheet is performed by bonding the adhesive surface of the laminated rubber sheet and the prepreg layer. Adhesive strength is improved by the reaction between the uncrosslinked or semi-crosslinked rubber of the laminated rubber sheet and the uncured reactive group of the prepreg layer.

The method of laminating the prepreg and laminated rubber sheet is set up using a lamination jig such as an alumite plate or a release metal plate such as duralumin, or a cushion plate, by overlapping the prepreg and laminated rubber sheet. A method of inserting between hot plates of a hot press and performing a laminating adhesive press is preferable. As conditions for the lamination adhesive press, appropriate conditions that do not impair the integrity of the laminate, for example, conditions of a press surface pressure of about 30 to 150 kg / cm ² , a temperature of about 100 to 200 ° C., and a pressing time of about 30 minutes to 6 hours. Can be done.

As for the thickness of the laminated body of this invention, 0.5-5 mm is preferable.
The laminate of the present invention can be used as a sealing material for electrolytic capacitors, a sealing material for precision products that enclose liquids and gases, various packings, insulating sheets, protective sheets, and the like.

Examples 1 to 5 and Comparative Examples 1 to 3
Ethylene-propylene rubber (manufactured by JSR Corporation, trade name EP65, represented as EPDM in Table 1) as a rubber, and trimethylolpropane triacrylate (as a compound having a plurality of polymerizable unsaturated double bonds in the molecule) Shin-Nakamura Chemical Co., Ltd., trade name NK Ester A-TMPT), carbon black (made by Tokai Carbon Co., trade name 116), clay (Burgess Pigment, trade name Burgess) # 30), an organic peroxide (manufactured by NOF Corporation, trade name Perhexa 25B-40) was prepared, kneaded according to the formulation shown in Table 1, and then formed into a sheet shape with a calendar roll, with a thickness of 1 mm. An uncrosslinked rubber sheet was obtained.
This uncrosslinked rubber sheet was irradiated with an electron beam under the conditions shown in Table 1 to obtain a laminated rubber sheet. In Table 1, Example 3 is a reference example.

The laminated rubber sheet adhesive layer and the prepreg (resole type phenol resin impregnated paper) are overlapped and laminated and bonded under the conditions of a pressing surface pressure of 100 kg / cm ² , a temperature of 170 ° C. and a pressing time of 1 hour. A laminate having a thickness of 2.5 mm was obtained.
The obtained laminate was cut to a width of 25 mm, and a 180 ° peel test was performed according to JISK6256. The peel test was performed at the interface between the rubber sheet and the prepreg, and the state of the adhesive surface was observed. The case where the rubber sheet and the prepreg were delaminated was evaluated as x, and the case where the rubber sheet layer was peeled or broken was evaluated as ◯.
Further, as a confirmation of the dimensional change of the rubber, a change rate of the rubber sheet dimension after the lamination adhesion to the rubber sheet dimension before the lamination adhesion was measured using a square rubber sheet dimension having a side of 150 mm. A case where the rate of change was 20% or less was evaluated as ◯, and a case where the rate of change exceeded 20% was evaluated as ×.
The results are also shown in Table 1.

表１に示すように、各実施例の積層体は優れた接着強度および２０％以下の寸法変化率を示した。

As shown in Table 1, the laminate of each example exhibited excellent adhesive strength and a dimensional change rate of 20% or less.

  Since the laminated body using the rubber sheet for laminated bodies of this invention is excellent in adhesive strength, it is excellent in sealing performance. Therefore, it can be used as a sealing material for electrolytic capacitors and a sealing material component for precision products that enclose liquid or gas.

Claims (4)

A rubber sheet for a laminate laminated on a prepreg,
The rubber sheet has a Mooney viscosity (ML _{1 + 4} 125 ° C.) of 50 to 100 when uncrosslinked, and the non-adhesion is caused by at least electron beam irradiation from the non-adhesive surface side opposite to the adhesive surface in contact with the prepreg. A rubber sheet for a laminate , wherein a surface side is cross-linked and the adhesive surface side is uncrosslinked .   The rubber sheet for a laminate according to claim 1, wherein the rubber sheet contains a compound having a plurality of polymerizable unsaturated double bonds in the molecule.   The rubber sheet for a laminate according to claim 2, wherein the compound having a plurality of polymerizable unsaturated double bonds in the molecule is a (meth) acrylic acid ester of a polyhydric alcohol. A laminate of a prepreg and a rubber sheet,
A laminate, wherein the rubber sheet is the rubber sheet for laminate according to claim 1, claim 2, or claim 3 .