JPH085154B2 - Structural material made of synthetic resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a synthetic resin structural material that is lightweight, has excellent heat insulating properties, and has high strength.

(Prior Art) Since synthetic resin has the characteristics of being lightweight and resistant to corrosion,
Attempts have long been made to use it as a structural material. However, synthetic resins generally have the drawback of poor strength. Therefore, in order to make up for this, glass fibers or carbon fibers are mixed into a synthetic resin to form a fiber-reinforced resin. Although the fiber-reinforced resin is certainly rich in strength and rigidity, it has lost the advantage of being lightweight because it contains glass and carbon.

In order to improve this, Japanese Patent Laid-Open No. 1-156051 discloses
It has been proposed that a synthetic resin foam is used as a base material and a fiber-reinforced layer of resorcin-based resin is provided on one or both surfaces of the base material. However, there has only been considered to use a polystyrene foam or a soft polyurethane foam as the synthetic resin foam. However, these foams are originally soft, or even if they are hard, they soften at 100 ° C, and the resorcin-based resin forms a resin layer unless heated to 100 ° C or higher while being pressurized. In the end, this proposal does not allow the fiber reinforcement layer to adhere to the foam while maintaining the original system. Therefore, according to this proposal, a strong and lightweight synthetic resin structural material could not be obtained. Therefore, the advent of a further improved structural material has been demanded.

(Problems to be Solved by the Invention) The present invention has been made in order to provide a synthetic resin structural material which is lightweight, has excellent heat insulating properties, and has high strength.

(Means for Solving the Problem) When the resin constituting the foam is polystyrene or soft polyurethane, the present inventor has suggested that when the resin is heated to cure the resorcin resin, the foam is deformed. However, if a thermoplastic polyester resin is used as the resin forming the foam, the foam will not be deformed even when heated to a temperature at which the resorcin-based resin or other thermosetting resin is cured. I found that there is no.

Here, the thermoplastic polyester resin (hereinafter referred to as PAT) is a high molecular weight chain polyester produced by causing a condensation reaction between an aromatic dicarboxylic acid and a dihydric alcohol. A typical example thereof is polyethylene terephthalate produced by condensation of terephthalic acid and ethylene glycol.

Further, this inventor is not limited to the resorcin-based resin, a wide range of uncured thermosetting resin is brought into contact with the surface of the PAT foam, and the thermosetting resin is heated and cured. It was found that the thermosetting resin adheres strongly to the PAT foam by blending with the irregularities due to the bubbles on the foam surface. Furthermore, the present inventor has added reinforcing fibers such as glass fibers to the thermosetting resin, and the obtained molded product is reinforced by the fibers, and a tough molded product is obtained. I found that Based on such knowledge, the present inventor has proposed a structural material in which a fiber-reinforced thermosetting resin is integrally provided on one surface of the thermoplastic polyester resin foam (Japanese Patent Application No. -344250, JP-A-3-
199044).

However, it was found in the proposal that a thermosetting resin containing fibers was foamed to obtain a synthetic resin structural material which is lighter in weight, has excellent heat insulating properties, and has high strength. The present invention has been made based on such knowledge.

(Summary of the Invention) The present invention is a synthetic resin in which an uncured thermosetting resin containing a fiber and a foaming agent is brought into contact with at least one surface of a PAT foam to foam and cure the thermosetting resin to form an integrated resin. It concerns a structural material.

The PAT used in this invention is a high molecular weight chain polyester made from an aromatic dicarboxylic acid and a dihydric alcohol, as described above. As the aromatic dicarboxylic acid, in addition to terephthalic acid, isophthalic acid, 2,6
-Naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxy dicarboxylic acid can be used. Further, as the dihydric alcohol, in addition to ethylene glycol, trimethylene glycol, tetramethylene glycol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2-bis (4-β -Hydroxyethoxyphenyl) propane, 4,4'-bis (β-hydroxyethoxy) diphenylsulfone, diethylene glycol can be used. Such PAT is commercially available. In the present invention, commercially available PAT can be used.

PAT is said to be a resin that is difficult to foam. The reason is that PAT is a crystalline resin, and when it is heated, it softens rapidly and becomes a liquid with low viscosity.
That is, PAT has a narrow temperature range in which it has a viscosity suitable for foaming, and therefore it is difficult to maintain the foaming temperature at an appropriate level, and when the viscosity becomes low, the gas that acts as a foaming agent quickly dissipates. . It is for this reason that PAT foams are not widely known.

However, the difficulty of foaming is gradually being eliminated by subsequent improvements. For example, by mixing a diepoxy compound with PAT or adding a compound of a metal belonging to Group Ia or Group IIa of the periodic table, the difficulty of foaming is gradually overcome. Further, by adding an acid dianhydride such as pyromellitic anhydride, an epoxy compound such as diglycidyl terephthalate, or sodium carbonate to PAT, foaming is facilitated by improving the melting characteristics of PAT. It's starting.

The simplest method for producing PAT foam is to extrude and expand PAT. To do this, put PAT in the extruder and
The AT is heated and melted, the foaming agent is pressed into the melted PAT,
A mouthpiece provided with a slit-shaped extrusion hole may be attached to the tip of the extruder, and PAT may be extruded into the atmosphere through the extrusion hole. If the extrusion holes are slit-like, the PAT will be extruded in the form of a sheet, and if successfully foamed, it will be foamed several times.

For structural applications, PATs generally do not need to be so foamed. Therefore, the sheet foamed several times as described above is sufficiently durable to use. However, it does not prevent the use of large foams.

As the foam material, various materials can be used. Broadly speaking, solid compounds that decompose at a temperature above the softening point of PAT to generate gas, liquids or gases that vaporize in PAT when heated, inert gas that can be dissolved in PAT under pressure, etc. Either can be used. The above-mentioned solid compound is, for example, azodicarbonamide, dinitrosopentamethylenetetramine, hydrazocarbonamide, sodium bicarbonate and the like. The liquid or gas to be vaporized is, for example, saturated aliphatic hydrocarbons such as hexane, pentane, butane, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene and xylene, methylene chloride. , Halogenated hydrocarbons such as Freon (registered trademark). The inert gas is, for example, carbon dioxide or nitrogen. In addition, a high molecular weight chain aromatic polycarbonate can be used as the foaming agent as taught in JP-A-59-135237.

Various thermosetting resins can be used. For example, unsaturated polyester resin, epoxy resin and phenol resin can be used. Although all of these resins are in an uncured state, they may be in the form of powder or liquid.

The unsaturated polyester resin is a thermosetting resin in which a vinyl monomer is dissolved in a resin (base resin) obtained by a condensation reaction of unsaturated and saturated dicarboxylic acids with a divalent alcohol. An unsaturated group is contained in the main chain of the base resin, and this causes a copolymerization reaction with this and a vinyl-based monomer to crosslink and cure. Maleic anhydride and phthalic anhydride are often used as the dicarboxylic acid, ethylene glycol and propylene glycol are used as the dihydric alcohol, and styrene is used as the vinyl-based monomer. The uncured product of this resin is obtained as a powdery or low-viscosity liquid.

The unsaturated polyester resin is added with an organic peroxide such as benzoyl peroxide and is cured when heated to form a hard resin. At this time, if a curing accelerator such as dimethylaniline or cobalt naphthenate is added, curing is performed without heating. Also, this resin forms a layer without pressure.

The epoxy resin is a resin having two or more epoxy groups in the molecule. This resin is classified into various types such as bisphenol A type, cycloaliphatic type and those derived from polybutadiene. Among them, the bisphenol A type is often used. .
This is the general formula Is a resin represented by. Here, n is an integer of 0-12. Depending on the number of n, there are various stages from liquid to solid. This is an uncured product of epoxy resin.

When a curing agent is added to the uncured epoxy resin, it cures to form a hard resin. As the curing agent, aliphatic diamine, aromatic diamine, aromatic acid anhydride, aliphatic polyamide, etc. can be used. By adding an aliphatic polyamine, it can be cured at room temperature without heating,
When the aromatic diamine or aromatic acid anhydride is added, it is heated to cure. The curing can be performed under pressure, or can be performed under normal pressure without applying pressure.

Phenolic resins are resins made by the reaction of phenol with formaldehyde. Two kinds of resins having different chemical structures can be obtained depending on the catalyst used at that time. A resin obtained using an alkali as a catalyst is referred to as a resol, and a resin obtained using an acid as a catalyst is referred to as a novolak to distinguish them. Resol initially exhibits a liquid state, but when it is further heated, it becomes solid. Novolac is a brittle solid, to which hexamethylenetetramine is added as a curing agent, and when further heated, it cures to form a hard resin.

In the present invention, fibers are used to reinforce the thermosetting resin as described above. As the fibers, glass fibers, carbon fibers, aromatic polyamide fibers, metal fibers, potassium titanate fibers, silicon carbide fibers and the like can be used. The thickness of the fiber is set to several microns to several microns, and the length of the fiber can be various lengths as required. The state of the fibers may be monofilament, or may be any of yarn, strand, roving, chopped strand, mat, cloth and the like.

Further, in the present invention, in order to foam the thermosetting resin, when the resin is in an uncured state, a foaming agent is added to the resin to foam and cure the resin. Various kinds of foaming agents can be used. Broadly speaking,
Solid compounds that decompose and generate gas at a temperature above the curing temperature of the resin, and below the curing temperature of the resin are dissolved in the resin,
A liquid or gas that vaporizes in the resin when the temperature exceeds the curing temperature of the resin can be used. The above-mentioned solid compound is, for example, 2,2'-azoisobutyronitrile, diazoaminobenzene, terephthal azide or the like. The vaporizable liquid or gas is, for example, petroleum ether, acetone or the like.

The uncured thermosetting resin containing the fiber and the foaming agent can be easily prepared by mixing the fiber and the foaming agent with the resin. When an unsaturated polyester resin is used as the curable resin, a mixture obtained by impregnating what is called a sheet molding compound, generally called SMC, with a foaming agent can be used as it is.

The structuring agent according to the present invention, a PAT foam is contacted with a thermosetting resin containing a fiber and a foaming agent, and thereafter,
Giving a space where resin can be foamed in the direction perpendicular to the contact surface between the PAT foam and thermosetting resin, and heating the resin,
You can make this. No special adhesive need be used on the foam. However, when pressure is required to adjust the shape when curing the thermosetting resin, the thermosetting resin is put into a press and pressed. However, PAT foam is usually 200
Since it does not soften at temperatures up to ° C, it does not deform when heated to cure the thermosetting resin. In addition, since the PAT foam hardly deforms even when a slight pressure is applied, it hardly deforms even if it is pressed when the resin is cured. Even if it is strongly pressed, the PAT foam only elastically deforms and does not lose the foam structure. In this way, a structural material in which the fiber-containing foamed resin and the PAT foam are integrated can be easily and reliably manufactured.

The fiber-containing foamed resin may be attached to only one side of the PAT foam, but it is also attached to both sides, and the fiber-containing foamed resin sandwiches the PAT foam inside to form a sandwich structure. Good.

(Effect of the invention) According to the present invention, since PAT is used as the material of the foamed body, since PAT has heat resistance that does not soften up to 200 ° C, a thermosetting resin is foamed on this surface and Even when cured, the foam does not lose its foam structure, and therefore the thermosetting resin layer can be directly provided on the foam. Moreover, in this case, since the surface of the foam has unevenness due to bubbles, the thermosetting resin strongly adheres to the foam, and thus the product obtained is difficult to peel off. Further, since the thermosetting resin contains fibers, it is reinforced with fibers and has sufficient mechanical strength. Moreover, it is easy to manufacture because no special adhesive is required to make it. In addition, the products made in this way are lighter and have better heat insulation because the thermosetting resin and PAT that make them up are also foamed. Since all the fiber-containing thermosetting resins have sufficient heat resistance and mechanical strength, the entire product is lightweight, has excellent heat insulating properties, and has high strength. Therefore, this product is
Suitable for use as a structural material, for automobiles, aircraft,
It is suitable for use as a structural material for ships and the like.

(Examples) Hereinafter, the reason why the structural material according to the present invention is excellent will be specifically described with reference to Examples and Comparative Examples. In the following, simply "parts" means "parts by weight".

Example 1 (Structure of PAT Foam) As PAT, 100 parts of polyethylene terephthalate pellets (TR8580 manufactured by Teijin Ltd.) having an intrinsic viscosity of 0.81 were used, and the PAT was 5 at a dew point of −20 ° C. and hot air of 160 ° C. After drying for an hour, 0.33 parts of pyromellitic dianhydride was added,
0.1 parts of sodium carbonate (both PAT viscosity modifiers) and 0.6 parts of talc powder (bubble modifier) were added, and the mixture was put in a tumbler and mixed well, and then put into an extruder.

The extruder had a cylinder temperature of 274-287 ° C and a die temperature of 277 ° C. Also, butane as a foaming agent was pressed in at a ratio of about 1.0 part from the middle of the cylinder.

A die with an annular slit is attached to the tip of the extruder, PAT containing butane is extruded into a cylindrical shape from the annular slit, and while propagating the PAT, it advances on a cylindrical mandrel and foams. I made a sheet. After that, this was cut open to form a flat sheet and wound into a roll. The obtained foamed sheet had a density of 0.2 g / cm ³ and a thickness of 3 mm. From this, a square sheet having a side of 150 mm was cut out and used as a PAT foam sheet.

(Fiber and foaming agent-containing thermosetting resin) A glass fiber mat with a weight per 1 m ² (hereinafter referred to as “weighing”) of 300 g (FEM-300, manufactured by Fuji Fiber Glass Co., Ltd.)
-04) in a 150 mm square, 30 g of phenolic resin (PF-0015 made by Asahi Organic Materials Co., Ltd., viscosity 5100CP / 25 ° C), 5 g curing agent (made by the same company, CA-645), and foaming agent (made by the same company, AA -30) A mixture with 3.6 g was uniformly impregnated into an uncured thermosetting resin sheet containing fibers and a foaming agent. I made two sheets like this.

(Production of Structural Material) A PAT foam sheet was sandwiched between the above-mentioned uncured thermosetting resin sheet containing fibers and a foaming agent, and the superposed product was placed in a mold. The formwork was a square metal plate with a thickness of 5 mm and a side of 180 mm, and a square with a side of 150 mm was punched out in the center, forming a square frame with a width of 15 mm. . The stack placed in the formwork left a space in which it could expand in the thickness direction of the sheet. Put the formwork containing the stack in the press, 40kg / c
A structural material was obtained by heating at 90 ° C. for 20 minutes while applying a pressure of m ² .

The obtained structural material had a thickness of 5 mm and a density of 0.75 g / cm ³ . When the bending strength of the structural material was measured according to JIS K 7203, the bending strength was 292 kg · f / cm ² and the amount of deflection was 12.4 mm. The elastic modulus was 19400 kgf / cm ² . In addition,
I tried to peel it off at the interface between the phenol resin layer and PAT,
It did not come off easily. From this, it was confirmed that this structural material can be sufficiently used as a structural material for automobiles, aircrafts, and ships.

Comparative Example 1 A structural material was prepared in the same manner as in Example 1 except that the use of the foaming agent mixed with the phenol resin was stopped.

The obtained structural material had a thickness of 5 mm and a density of 0.75 g / cm ³ . The structural material has a bending strength of 254 kgf / cm ² and a bending amount.
The elastic modulus was 6.93 mm and 22800 kgf / cm ² . As a result, it could be used as a structural material, but was less flexible than that of Example 1.

Example 2 In this example, the compounding ratios of the fiber and the foaming agent-containing thermosetting resin were changed from Example 1, but the same PAT foam as in Example 1 was used, and the PAT foam and thermosetting resin were used. It was carried out by changing the bonding conditions with the resin sheet.

More specifically, the phenolic resin (PF-
) 19g, curing agent (CA-645) 2.8g, foaming agent (AA-
30) The glass fiber mat (FEM-300-04) used in Example 1 was impregnated with a mixture of 1 g and an uncured thermosetting resin sheet, and two such sheets were prepared. The same PAT foam as that used in Example 1 was sandwiched between these sheets and pressed at 80 ° C. for 30 minutes at a pressing pressure of 35 kg / cm ² to obtain a structural material.

The obtained structural material had a thickness of 5 mm and a density of 0.59 g / cm ³ . The bending raw load is 21.2kgf and the bending strength is 302k.
g ・ f / cm ² , deflection is 10.9 mm, elastic modulus is 14900 kg ・ f / cm ^2.
Met.

Comparative Example 2 A structural material was prepared in the same manner as in Example 2 except that the use of the foam material mixed with the phenol resin was stopped.

The obtained structural material had a thickness of 5 mm and a density of 0.59 g / cm ³ . The bending raw load is 15.3kg ・ f and the bending strength is 222k.
g ・ f / cm ² , deflection is 7.64mm, elastic modulus is 21400kg ・ f / cm ²
Met.

Example 3 (Structure of PAT foam) From the foamed sheet (density 0.2 g / cm ² , thickness 3 mm) obtained in Example 1, 5 square sheets each having 250 mm on a side were cut out. Three of these sheets were stacked, and a stacked product was sandwiched between each sheet with a square of 250 mm on a side and a thickness of 50 μ of polyester hot melt film (PS-2810: manufactured by Daicel Chemical Industries). Put in, 0.2kg / cm
While applying a pressure of ^2, it was heated for 2 minutes at 180 ° C., 1 primary PA
A T laminate was obtained. In addition, the remaining 2 at both ends of this primary PAT laminate
A sheet of polyester hot-melt film (PS-28) with a side of 250mm square and a thickness of 50μ is put between each structural material and the sheet in the same manner as above.
10: manufactured by Daicel Chemical Co., Ltd.) was put in a press and heated at 180 ° C. for 2 minutes while applying a pressure of 0.2 kg / cm ² , to obtain a secondary PAT laminate.

Since the PAT sheet itself is a heat insulator, the reason why the PAT sheet itself is a heat insulator is that the inner layers do not adhere to each other if they are stacked too much.

(Fiber and foaming agent-containing thermosetting resin) A 250 mm square glass fiber mat (FEM-300-04, manufactured by Fuji Fiber Glass Co., Ltd.) weighing 300 g / m ² and a phenol resin (Asahi Organic Materials Co., Ltd., PF -0015, viscosity 5100cp / 25
192 g), a mixture of a hardening agent (manufactured by the same company, CA-645) 29 g and a foaming agent (manufactured by the same company, AA-30) 12 g, and uniformly impregnated,
This was made into an uncured thermosetting resin sheet containing fibers and a foaming agent. I made two sheets like this.

(Production of Structural Material) A PAT foam sheet was sandwiched between the above-mentioned uncured thermosetting resin sheet containing fibers and a foaming agent, and the superposed product was placed in a mold. The formwork has a thickness of 28 mm and a side of 280 mm
A square metal plate with a side of 250 mm in the center, which is a frame-shaped object with a width of 15 mm.
It was a square frame. The stack placed in the formwork left a space in which it could expand in the thickness direction of the sheet. Put the formwork containing the stack in the press, 45 kg
While applying a pressure of / cm ² , it was heated at 80 ° C for 30 minutes to obtain a structural material.

The structural material obtained has a thickness of 28 mm and a density of 0.41 g / cm ³
Met. Its thermal conductivity is 0.0339Kcal / m ・ hr ・ 20 ℃
° C.

Comparative Example 3 PAT foam was not used in this comparative example.

(Fiber and foaming agent-containing thermosetting resin) A 250 mm square glass fiber mat (FEM-300-04, manufactured by Fuji Fiber Glass Co., Ltd.) weighing 300 g / m ² and a phenol resin (Asahi Organic Materials Co., Ltd., PF -0015, viscosity 5100cp / 25
℃) 330g, a curing agent (manufactured by the same company, CA-645) 50g and a mixture of a foaming agent (manufactured by the same company, AA-30) 17.5g are uniformly impregnated, and this is uncured containing fibers and a foaming agent. Of the thermosetting resin sheet. I made two sheets like this.

(Production of Structural Material) Two uncured thermosetting resin sheets containing the above fibers and a foaming agent were superposed and placed in a mold. The formwork is similar to that used in Example 3. The stack placed in the formwork left a space in which it could expand in the thickness direction of the sheet. Put the formwork containing the stack in the press,
While applying a pressure of 45 kg / cm ² , heat at 80 ° C for 30 minutes,
A structural material was obtained.

The resulting structural material has a thickness of 28 mm and a density of 0.42 g / cm ³
Met. Its thermal conductivity is 0.0494Kcal / m ・ hr ・ 20 ℃
° C.

Claims (1)

[Claims] 1. An uncured thermosetting resin containing a fiber and a foaming agent is brought into contact with at least one surface of a foamed body of a thermoplastic polyester resin, and the thermosetting resin is foamed and cured to be integrated. Structural material made of synthetic resin.