JPH0416337A - Epoxy resin foamable sheet, foamed cured body and composite material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is easy to work with and can be used as a foam by foaming and hardening, or can be foamed and hardened by being sandwiched between molding molds to form a composite material. The present invention relates to a foamable sheet with excellent properties, a foam cured product using the same, and a composite material.

<Prior art> Conventionally, epoxy resin foams have been produced by adding organic blowing agents such as azodicarbonamide and azobisisobutyronitrile, inorganic blowing agents such as sodium bicarbonate, or water and fluorocarbons to the epoxy resin/epoxy curing agent system. A method of blending a compound such as the above and foaming it by heating or self-curing heat generation is known.

Furthermore, foamable sheets in which nonwoven fabric is impregnated with these foamable resins are also known.

However, these sheets lacked flexibility, and the resin was easily removed from the nonwoven fabric during processing such as cutting and bending. Furthermore, the cured product after foaming also lacked toughness.

When making composites of these foams and other materials, it is necessary to bond the cured foam and other materials with an adhesive, which complicates the work process and may result in insufficient adhesion. there were.

<Problems to be Solved by the Invention> The present invention attempts to solve the above-mentioned problems of the prior art. It is an object of the present invention to provide a foamable epoxy resin sheet that has good toughness and excellent workability, and a foam cured product and a composite material using the same.

<Means for Solving the Problems> Therefore, the present invention consists of (1) a polyepoxy compound having two or more epoxy groups in one molecule, (2) a carbonate oligomer having a phenolic hydroxyl group at the end, and (2) a reaction catalyst. To provide a foamable epoxy resin sheet, characterized in that the epoxy resin composition contained therein is impregnated or fused to a cloth-like material in a semi-cured (B stage) state.

Further, the present invention provides the above-mentioned foamable sheet by itself.
Alternatively, the present invention provides a foamed cured product and a composite material obtained by heating and foaming and curing together with other materials.

Here, it is preferable that the epoxy resin composition further contains (1) short fibrous material.

The present invention will be explained in detail below.

The epoxy resin composition used in the present invention has:
A polyepoxy compound having 1 or more epoxy groups;
It contains a carbonate oligomer having a phenolic hydroxyl group at the end and (2) a reaction catalyst.

■Polyepoxy compounds having two or more epoxy groups in one molecule include bisphenol A1 tetrabromobisphenol A, bisphenol F1 bisphenol aldehyde, polyphenols, diglycidyl ether epoxy resins such as resorcinol and hydroquinone, and polyalkylenes. Examples include polyglycidyl ether-based epoxy resins such as glycol and phenol resin, and polyglycidyl ester-based epoxy resins of polycarboxylic acids such as phthalic acid. Preferably, a bisphenol type polyepoxy compound is used.

These polyepoxy compounds can be either liquid or solid at room temperature. Epoxy resin, which is liquid at room temperature, is usually used to impregnate cloth-like materials at room temperature.
A solvent or a low-viscosity epoxy compound can be used as a diluent to adjust the impregnation properties. As solvents, aromatic hydrocarbons such as toluene and xylene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and ethylene glycol ethers such as methyl cellosolve and ethyl cellosolve can be used. For low viscosity epoxy compounds,
Mainly used are mono- or diglycidyl ethers having 3 to 15 carbon atoms such as N-butylglycidyl ether, and aromatic mono- or diglycidyl ethers such as phenylglycidyl ether.

For resins that are solid at room temperature, the preferred softening point is 60.
℃ to 130°C, and if the temperature is 130°C or higher, a high temperature is required during mixing with other raw materials and impregnation, and the workability for keeping the material in the B stage deteriorates.

These polyepoxy compounds are usually 0. It contains 1 to 08% by weight of water, and may also contain about 3 to 20 mmol per 100 g of α-diol ring-opened by water, that is, about 5 to 15% by weight.

It is thought that such water or α-diols are involved in the reaction during the production reaction of the epoxy resin foamable sheet in the present invention.

In addition, when using a polyepoxy compound that is in a dry state and does not contain water or α-diol, water or α-diols must be added as a reaction aid when mixing with the carbonate oligomer described below. good.

(2) A carbonate oligomer having a phenolic hydroxyl group at the end is usually represented by the following formula.

(In the formula, Ar is a divalent phenol residue such as a phenyl group or bisphenyl. n indicates the number of repeats.) The preferable value of n is a value determined by C-NMR analysis, and is 0 to 0. 10, and the preferred hydroxyl equivalent is 100-
It is 2800.

Such carbonate oligomers can be used in an amount of 1 to 60 parts by weight per 100 parts by weight of the polyepoxy compound,
When low foaming is required, 1 to 10 parts by weight is used, and when higher foaming is required, 30 to 60 parts by weight is used, and for normal foaming, 10 to 30 parts by weight is preferred.

(2) Examples of the reaction catalyst include tertiary amines, imidazoles, onium salts, trialkylphosphines, and triarylphosphines. Specifically, imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole, onium salts such as choline chloride and tetramethylammonium chloride, tris(N,N-dimethylaminomethyl)phenol, N , N-benzylmethylamine, 1,8-cyasabicyclo(5,4,0)undecene, etc. and their conductors, as well as tri-N-propylphosphine, tri-N-butylphosphine, triphenylphosphine, etc. are used.

Preferred are imidazoles and trialkylphosphines, more preferred are imidazoles.

It is preferable to add these reaction catalysts in an amount of 0.05 to 5.0 parts by weight based on 100 parts by weight of the polyepoxy compound, since the curing properties coincide with the foaming timing.

In addition, addition of 0.01 to 1 part to 2 parts of the above-mentioned α-diol and water as effective reaction aids is useful when foaming and curing an epoxy resin foam sheet to form a cured product. This results in an increase in t, which may be preferable.

Here, the α-diol includes, for example, algylene glycol. Other reaction aids include polyol compounds having two or more vicinal hydroxyl groups, such as glycerin.

(2) In the present invention, a short fibrous material may be further added to the epoxy resin composition composed of (1) to (4) above. By adding short fibers, it is possible to obtain an epoxy resin foam sheet with higher bending resistance and excellent workability, and the cured foam material using this sheet also has high mechanical strength. Examples of the shaped material include short fibers such as natural cellulose, plastic, and glass, and whiskers made of silicon carbide, titanium, alumina, boron, steel, and the like.

This short fibrous material was added in an amount of 100 parts by weight per 100 parts by weight of the polyepoxy compound, taking into consideration the reduction in bending resistance of the sheet.
It is best to add less than 1 part by weight. A blending amount of 100 parts by weight or more is not preferable because it lowers the bending resistance of the sheet.

Furthermore, if necessary, adding calcium carbonate, talc, barium sulfate, titanium dioxide, etc. as a filler in an amount of 100 parts by weight or less per 100 parts by weight of the polyepoxy compound can improve the modification of the epoxy foam produced. It may be connected and desirable.

Further, it is preferable to add an acrylic flow control agent and a silicone foam stabilizer together with the polyepoxy compound and oligomer.

The epoxy resin composition used in the present invention is obtained by mixing the above-mentioned polyepoxy compound, carbonate oligomer, reaction catalyst, necessary short fibers, other components, and the like.

When the polyepoxy compound etc. is solid, the softening temperature varies depending on the raw material mixture, but usually the temperature is 80 to 1.
Heat and melt mixing is performed using a roll or a kneader within a range of 20°C.

Within this temperature range, the foaming reaction hardly progresses, but the curing reaction progresses slowly, so the mixing time is usually within 5 minutes so as not to exceed the B stage, and the mixture is immediately cooled to room temperature and then crushed to form a powder. A composition.

In addition, when the polyepoxy compound etc. is in liquid form, in order to dissolve or disperse the raw material mixture, it is mixed in a container equipped with a stirrer at 30°C to 100°C or on a roll, and immediately cooled to form a liquid composition. Bye. The viscosity of the liquid composition is preferably viscous or semi-solid at room temperature in order to maintain stability after impregnation into a fabric.

The epoxy resin foam sheet of the present invention is obtained by impregnating or fusing the above-mentioned epoxy resin composition into a cloth-like material in a semi-cured (B stage) state.

The cloth-like material may be porous and capable of sufficiently impregnating or fusing the epoxy resin composition, or it may have a sandwich structure in which both sides are sandwiched between cloth-like materials so that the epoxy resin composition can be retained at 120°C. Those having the above heat resistance are preferable. For example, polyester, polypropylene nonwoven fabric, natural fiber mat, coarse mesh cloth, etc. can be used.

The temperature at which the epoxy resin composition is impregnated or fused is between room temperature and 80°C in the case of a liquid composition, and the viscosity of the composition is changed to adjust the impregnating property to the cloth-like material. I can do it. Furthermore, it is passed through a heating furnace at 80° C. to 150° C., and the B-stage reaction is advanced by adjusting the temperature and time.

When the epoxy resin composition is in powder form, it is fused to a cloth at a temperature of 60°C to 150°C, which is equal to or higher than the softening point. After impregnation or fusing, it is preferable to immediately cool the film to room temperature.

An example of the method for manufacturing the epoxy resin foam sheet of the present invention is shown in FIG. 1a, FIG. 1b, and FIG. 2. In FIG. 1a, a metal vat 5 is filled with a liquid composition 1 heated between room temperature and 80° C., and a cloth 2 supported by scissors 4 is immersed therein. The cloth-like material 2 impregnated with the composition is passed between squeeze rolls 3 to remove excess composition, and then heated in a heating oven for 80 minutes.
Perform the B-staging reaction at ~150°C for 2-15 minutes.

The reaction conditions are selected by testing the gelation conditions of the liquid composition alone in advance and setting the conditions before gelation. For example, for a liquid composition that gels in 10 minutes at 120°C, it is preferably 5 to 10 minutes at 100°C or 5 minutes at 120°C.

By immediately cooling to room temperature after the reaction, an epoxy resin foamable sheet that can be stored for a long period of time can be obtained.

FIG. 1b shows an apparatus for continuously impregnating a liquid composition, in which a continuously moving cloth 2 is impregnated with the liquid composition in an impregnating tank 6 containing the liquid composition, and the excess is removed by a squeezing roll 3. After the composition is dropped, it is turned into a B stage by a heating furnace 7, transferred to a cooling tank 8, cooled, and wound up by a winder 9. If the adhesive remains on the cloth-like material 2 after passing through the cooling tube 8, a release paper 10 may be inserted for 4f.

The thickness of the resulting epoxy resin foam sheet can be adjusted within a range of 2 mm or less by adjusting the thickness of the fabric, the viscosity of the liquid composition, and the gap between the L ff rolls, and this adjustment depends on the expansion ratio of the liquid composition. Determined by the required dimensions after foaming and curing. If a thickness of 2 mm or more is required, the purpose can be achieved by laminating multiple layers.

FIG. 2 shows an example of a manufacturing method in which a powdery composition is fused and impregnated into a cloth-like material. The cloth-like material 2, the powder composition 13, and the cloth-like material 2 are sequentially laminated in the mold 11, and pressed in the direction shown by the arrow 14 using a press or the like. By heating and pressing, the powder composition 13 and the cloth-like material 2 are fused and impregnated. Further, the cloth-like material 2 may be provided only on one side of the wire-like composition 13. In the pressing, heat is applied at 60 to 150°C, and the pressing time is set before gelatinization at the above temperature, that is, within the B stage. Powdered composition 13 in advance so as to remain in the
It is desirable to test the gelation time of

Note that during pressing, the melted powder composition may ooze out from the cloth-like outer layer of the epoxy resin foam sheet, so if a release agent is applied to the inner surface of the mold, the resulting epoxy Convenient for taking out resin foam sheets.

The epoxy resin foam sheet of the present invention is highly flexible,
Even when cut, bent, or bent, the epoxy resin composition does not fall off from the fabric, and since it is in a semi-cured (B stage) state, it can be processed or transported in the form of a thin plate by itself.

Furthermore, from the epoxy resin foamable sheet of the present invention, foamed cured products and composite materials can be manufactured with good workability as follows.

The foamed cured product of the present invention comprises an epoxy resin foamable sheet,
Furthermore, it is a cured product obtained by heating and foaming and curing. When the epoxy resin foam sheet is further heated, the epoxy groups, carbonate oligomers, etc. undergo a crosslinking reaction, and carbon dioxide is released during the reaction, and this carbon dioxide acts as a foaming agent, so that it can be made into a foam.

As a result, the resulting foam has a uniform foaming state and is superior in flexibility, heat resistance, and adhesiveness compared to epoxy resin foams produced by conventional manufacturing methods.

Furthermore, since there is no need to add a blowing agent in addition to the polyepoxy compound and carbonate oligomer, the manufacturing process is simplified and economical.

Before foaming and curing, the foamed cured product can be processed and transported in the form of a thin plate as an epoxy resin foamable sheet, and can be used as a foamed cured product by being foamed at a desired location by heating. Is hardened foam a soundproofing material? It can be used as a shock absorbing acid absorbing material.

The composite material of the present invention is a composite material obtained by heating and foaming an epoxy resin foam sheet while contacting it with a molding die, and curing the sheet. When multiple epoxy resin foam sheets are laminated together or with other materials such as metal plates, and the sheets are foamed and cured while in contact with each other, at the same time as foaming occurs, the resin that seeps out of the fabric adheres to the metal plate, etc. In particular, strong composite materials can be obtained without using adhesives.

To cure the foam by heating, cut the epoxy 8J resin foam sheet to the specified size, set it in a mold press, etc., and press it for 14 minutes.
Preferably, it is heated to 0-200°C.

Other materials used for the composite material include steel plates, tinplates, wooden plates, etc., and the thickness and shape of the other materials and the thickness and shape of the epoxy resin foam sheet can be arbitrarily selected to create a glossy finish. A composite material with a desired shape can be obtained by adjusting the number of laminated sheets of other materials and epoxy resin foam sheets, and by adjusting the mold dimensions.

The composite material of the present invention can be easily manufactured using an epoxy resin foam sheet without using adhesives compared to composite materials using conventional foams, and is suitable for industrial fields such as architecture, vehicles, and acoustics. used for.

<Examples> Examples of the present invention will be shown below and explained in more detail.

(Example 1) Production of a foamable epoxy resin sheet ■ 100 parts by weight of a bisphenol A liquid epoxy resin having an epoxy equivalent of 189 was transferred to a container equipped with a stirrer and heated to 70°C. This was crushed with a hydroxyl equivalent of 295 and a softening point of 7.
40 parts by weight of bisphenol carbonate oligomer at 2°C and 20 parts by weight of methyl cellosolve as a solvent were added and melted.

Next, 1 part by weight of each of 1-benzyl-2-methylimidazole, an acrylic flow control agent, and a silicone foam stabilizer, and 10 parts by weight of potassium titanate short fibers were added and dissolved and dispersed. This mixture has a viscosity of 20 at room temperature.
It was Boyz.

The epoxy resin foam sheet was manufactured by the method of impregnating a cloth-like material as shown in FIG. 1a. Flat bat (vertical 35
1,200 g of the mixture was poured into a 25 cm-side polyester nonwoven fabric (basis weight 80 g/m2). The impregnated nonwoven fabric was passed through a squeezing roll and then B-staged in an oven at 110°C for 10 minutes to obtain an epoxy resin foam sheet. This epoxy resin foam sheet has a thickness of approx.
mm, and the resin content did not fall off from the nonwoven fabric due to bending or impact, and the workability was good.

Separately, an epoxy resin foam sheet was continuously produced from the mixture obtained above using the apparatus shown in FIG. 1b. The moving speed was adjusted so that the continuously moving nonwoven fabric passed through an impregnating tank, a squeezing roll, and then a heating furnace controlled at 110° C. for 5 minutes. The sheet after the reaction has some adhesiveness, so when winding it up, use release paper 1
Inserted 0.

(Example 2) Production of foamable sheet ■ 80 parts by weight of bisphenol A liquid epoxy resin with an epoxy equivalent of 1189, 20 parts by weight of propylene glycol diglycidyl ether with an epoxy equivalent of 150, a bisphenol type with a hydroxyl equivalent of 320 and a softening point of 76°C. 25 parts by weight of carbonate oligomer, 2-undecylimidazole,
1 part by weight of each silicone foam stabilizer and 5 parts by weight of polyester short fibers were added and dissolved and dispersed at room temperature. An epoxy resin foam sheet was obtained in the same manner as in Example 1 except that a polyester nonwoven fabric (basis weight: 40 g) was used as the cloth-like material.

In addition, in the B-stage process, the ff1Y! A foamable sheet in which the resin component did not fall off was obtained by i.

(Example 3) Production of foamable sheet ■ 100 parts by weight of a bisphenol type solid epoxy resin having an epoxy fi 920 and a softening point of 95°C, 30 parts by weight of a bisphenol carbonate oligomer having a hydroxyl group equivalent of 320 and a softening point of 76°C, and reacted. A mixture of 0.2 parts by weight of 2-methyl-imidazole as a catalyst, 0.5 parts by weight of an acrylic flow modifier, and 1 part by weight of a silicone foam stabilizer was mixed with an 8-inch roll heated to 110°C. Kneaded for 3 minutes. After cooling to room temperature, the obtained kneaded product was pulverized to obtain a powdery kneaded product that could pass through about 30 meshes.

Next, a polyester nonwoven fabric (basis weight 25 gefi12) was placed in a square mold with a side length of 30 cm as shown in Figure 2.
was placed thereon, and 180 g of the obtained powdery kneaded material was dispersed thereon. Furthermore, place another sheet of non-woven fabric on the top surface, and
The powdery kneaded material and the nonwoven fabric were fused together by pressing with a press machine at ℃.

As a result, the powdery kneaded product was molded into a sheet, and a foamable sheet with a thickness of about 2 mm and reinforced with nonwoven fabric on both sides was obtained (Example 3-1).

The thickness can be adjusted by adjusting the amount of the powdery kneaded material. For example, with 270 g of the powdery kneaded material, a foamable sheet with a thickness of about 3 mm was obtained (Example 3-2).

This thickness is determined by the required thickness after foaming.

(Example 4) Production of foamable sheet ■ 100 parts by weight of a bisphenol solid epoxy resin with an epoxy equivalent of 920 and a softening point of 95°C, 20 parts by weight of a bisphenol-based carbonate oligomer with a hydroxyl equivalent of 320 and a softening point of 76°C, 20 parts by weight of short glass fibers (diameter 5μ, length 150μ (average)), 0.2 parts by weight of 2-methyl-imidazole as a reaction catalyst, 0.5 parts by weight of acrylic flow modifier, and silicone. 1.0 parts by weight of a foam stabilizer was blended and kneaded for 3 minutes using an 8-inch roll heated to 110°C. After cooling to room temperature, the obtained kneaded product was pulverized to obtain a powdery kneaded product that could pass through about 30 meshes.

Next, in the same manner as in Example 3, a polyester nonwoven fabric (fabric weight R40 g/m2) was placed in a square mold with a side length of 30 cm.
was placed thereon, and 180 g of the obtained powdery kneaded material was dispersed thereon. A tin plate with a thickness of 0.24 mm coated with a mold release agent was placed on top of this and pressed with a press at 110° C. to fuse the powdery kneaded material and the nonwoven fabric. As a result of removing the tin plate, the powdery kneaded material was molded into a sheet shape, and a foamable sheet with a thickness of about 2 mm whose lower surface was reinforced with a nonwoven fabric was obtained (Example 4)
-1).

In addition, an epoxy resin foam sheet with a thickness of about 1 mm was obtained by adjusting the plate of the powdered kneaded material to i 00 g (
Example 4-2).

The obtained epoxy resin foam sheet had good workability, with the resin component not easily falling off due to bending or impact.

(Example 5) Production of a foamed cured product from a foamable sheet ■ 6 fffi foamable sheets obtained in Examples 1 to 4 were
The mixture was heated in an oven at 0° C. for 20 minutes to form a free-foamed cured product. The physical properties of this cured product are summarized in Table 1.

Table 1 (Example 6) Production of a foamed cured product from a foamable sheet ■ On a flat mold with a thickness of 10 mm and a side length of 30 cm
After placing a square metal frame and applying a mold release agent to the bottom surface, the foamable sheet obtained in Example 1 was cut into squares with sides of 30 cm, and one sheet was set in the mold frame. The upper surface was covered with a flat plate mold that had been subjected to mold release treatment, and heated with a 150 t hot press.

After 20 minutes, it was taken out from the mold to obtain a foam board with the same dimensions as the metal frame.

The properties of this foam board are shown in Table 2.

Table 2 (Example 7) Production of foamed cured product from foamable sheet■ S fff obtained in Examples 2 to 4 in the same manner as in Example 6
The foam sheets of type i were cut into squares with -sides of 30 cm, each sheet was set in a mold frame, and foamed and cured.

However, the thickness of the metal frame used was 80% of the average thickness of the sheet after free foaming shown in Table 1.

Obtained foam 5f! The characteristics of the class are shown in Table 2.

(Example 8) Production of a foamed composite material from a foamable sheet - A square metal frame with a side length of 30 cm and a thickness of 16 mm is placed on a flat mold; The foam sheet with a thickness of 2 mm obtained in Example 3 was sandwiched between two sheets (with a diameter of 0.24 mm) and set in a metal frame.

As a result of hot pressing at 150° C. for 20 minutes, the resin that oozed out from the nonwoven fabric at the same time as foaming bonded the metal plate, yielding a strong composite material consisting of three layers: metal plate/foam/metal plate.

Also, instead of the metal plate, 1.5 mm thick plywood 2
The foam sheet obtained in Example 4 was sandwiched between two sheets, and the thickness was 1
It was set in an 8mm metal frame. As a result of hot pressing at 170° C. for 20 minutes, a similarly strong composite material consisting of three layers was obtained.

Table 3 shows the properties of these composite materials.

Table 3 Ru.

<Effects of the Invention> The epoxy resin foam sheet of the present invention improves the brittleness of conventional foam resins, has toughness, and has good workability. If an epoxy resin foam sheet is used, it can be transported in a semi-cured state, and the sheet can be foamed and cured at a desired customer site to be used as a foam. In addition, by inserting the material into a mold and allowing it to foam and harden, it is possible to create a composite material with strong interlayer adhesion without the need for an adhesive.

[Brief explanation of the drawing]

FIG. 1a is a diagram illustrating an example of the method for manufacturing the epoxy resin foam sheet of the present invention. FIG. 1b is a diagram illustrating another example of the method for producing an epoxy resin foam sheet of the present invention. FIG. 2 is a sectional view illustrating another example of the method for producing an epoxy resin foam sheet of the present invention. Explanation of symbols 1... Liquid composition, 2... Cloth-like material, 3... Squeezing roll, 4... Scissors, 5... Metal bat, 6... Impregnation tank, 7...・Heating furnace, 8...-table a, 9... Winding machine, 10... Moving paper, 11... Mold, 13... Powdered composition, 14... Arrow FIG, 1a FIG, 1b

Claims (6)

[Claims] (1) An epoxy resin composition containing (a) a polyepoxy compound having two or more epoxy groups in one molecule, (b) a carbonate oligomer having a phenolic hydroxyl group at the end, and (c) a reaction catalyst. An epoxy resin foam sheet, characterized in that it is formed by fusing the above in a semi-cured (B stage) state to a cloth-like material. (2) The epoxy resin foamable sheet according to claim 1, wherein the epoxy resin composition further contains (d) short fibrous material. (3) An epoxy resin composition containing (a) a polyepoxy compound having two or more epoxy groups in one molecule, (b) a carbonate oligomer having a phenolic hydroxyl group at the end, and (c) a reaction catalyst. A foamed cured product obtained by heat-foaming and curing an epoxy resin foamable sheet that is fused to a cloth-like material in a semi-cured (B stage) state. (4) The epoxy resin foam cured product according to claim 3, wherein the epoxy resin composition further contains (d) short fibrous material. (5) An epoxy resin composition containing (a) a polyepoxy compound having two or more epoxy groups in one molecule, (b) a carbonate oligomer having a phenolic hydroxyl group at the end, and (c) a reaction catalyst. A composite material obtained by heating, foaming, and curing a foamable epoxy resin sheet obtained by fusing the epoxy resin to a cloth-like material in a semi-cured (B stage) state while contacting a molding die. (6) The epoxy resin foam cured product according to claim 5, wherein the epoxy resin composition further contains (d) short fibrous material.