JPH09208733A - Resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin foam excellent in weathering resistance and mechanical strength and hardly smoking in incineration and dumping. SOLUTION: This resin foam comprises an acrylic copolymer composed of 70-99.5wt.% of a methyl methacrylate monomer unit and 0.5-30wt.% of another copolymerizable monomer unit and having 7×10<4> to 50×10<4> weight - average molecular weight calculated as polymethyl methacrylate measured by gel permeation chromatography and 1.7-5 ratio of Z-average molecular weight calculated as polymethyl methacrylate/weight - average molecular weight calculated as polymethyl methacrylate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel resin foam. More specifically, it relates to a resin foam having excellent weather resistance and mechanical strength.

[0002]

2. Description of the Related Art Polystyrene, impact-resistant polystyrene, styrene-acrylonitrile copolymer resin, ABS resin and the like have been known as materials for resin foams. However, these foams made of a resin containing styrene as a main component are inferior in weather resistance and may be colored over time when used for outdoor applications such as building materials, so that the places to be used are strictly limited. In addition, when attempting to incinerate at the time of disposal, black smoke and soot are often generated, which is not preferable from the viewpoint of environmental problems.

A so-called acrylic resin containing polymethylmethacrylate as a main component is known as a resin for compensating the disadvantages of the polystyrene resin such as weather resistance and combustion behavior, but conventionally, a foam made of an acrylic resin, particularly a high foam is used. Has been difficult to form. The reason for this is not completely clear yet, but it is generally mentioned that the acrylic resin has a high melt viscosity and the melt has a low ductility. That is, when the molecular weight of the resin is lowered in order to lower the melt viscosity and improve the foamability and processability, the mechanical strength, solvent resistance and oil resistance of the foam are lowered.

On the other hand, when the processing temperature is raised to reduce the melt viscosity, methylmethacrylate monomer is generated due to thermal decomposition of the resin, and it is difficult to control the foaming rate and it is difficult to form a uniform foam. Furthermore, the acrylic resin is inferior in strength and ductility as a melt, and has a small ability to retain generated bubbles, so that it does not foam sufficiently and uniformly, and the foam surface is unlikely to be smooth. Therefore, the obtained foam was brittle and its appearance was inferior.

It has been proposed to use a methylmethacrylate-styrene copolymer as a resin that compensates for the drawbacks when these acrylic resins are used as foams (Japanese Patent Publication No. 51-2).
No. 4307, Japanese Patent Publication No. 51-27264), and the use of a methyl methacrylate-styrene copolymer having a specific solution viscosity index and a specific weight average molecular weight has also been proposed (Japanese Patent Publication No. 58-35613, Japanese Patent Publication No. 58-35613). Fair 7-
122001).

However, in these methods, since styrene is copolymerized, there is a problem that the weather resistance is still insufficient. Furthermore, in order to improve the impact resistance of the foam, it has been proposed to add a multi-layer structure polymer to the methyl methacrylate-styrene copolymer (Japanese Patent Publication No.
No. 7696), the improvement was still inadequate in terms of the uniformity and fragility of foaming.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a resin foam which is excellent in weather resistance and mechanical strength and emits less smoke when discarded by incineration.

[0008]

In order to produce an acrylic resin foam excellent in mechanical strength and appearance, the inventors of the present invention analyze the melting behavior of the resin and improve the ductility during melting. Since it is important to enhance the ability to retain bubbles and to make fine and uniform foaming, we have conducted intensive research. As a result, they have found that the use of an acrylic copolymer having a specific molecular weight distribution as a material has a remarkable effect particularly on the toughness and ductility during melting, and completed the present invention.

Hereinafter, the present invention will be described in detail. The present invention is composed of 70 to 99.5% by weight of a methyl methacrylate monomer unit and 0.5 to 30% by weight of another copolymerizable monomer unit, and is measured by gel permeation chromatography. From an acrylic copolymer having a methyl methacrylate-equivalent weight average molecular weight of 7 × 10 ⁴ to 50 × 10 ⁴ and a polymethylmethacrylate-equivalent Z average molecular weight / polymethylmethacrylate-equivalent weight average molecular weight ratio of 1.7 to 5. The present invention relates to a resin foam.

The acrylic copolymer in the present invention comprises 70 to 99.5% by weight of a methyl methacrylate monomer unit and 0.5 to 30% by weight of another copolymerizable monomer unit. Examples of other copolymerizable monomers include alkyl acrylates or alkyl methacrylates having an alkyl group having 1 to 18 carbon atoms, aromatic vinyl compounds such as styrene and nucleus-substituted styrene, acrylonitrile, methacrylonitrile, and the like. Examples thereof include vinyl cyan compounds, organic unsaturated acids such as acrylic acid, methacrylic acid, maleic acid and fumaric acid, maleic anhydride, maleimide, N-substituted maleimide and the like. These can be used alone or in combination of two or more kinds for copolymerization with methyl methacrylate.

As a material for the resin foam, if a large amount of gas such as a monomer is generated by thermal decomposition, the foaming rate cannot be controlled and uniform fine foaming cannot be achieved. In order to improve the thermal decomposability of the acrylic resin, in order to prevent depolymerization from the polymer terminal, the carbon number of the alkyl group is 1 to
Alkyl acrylates of 18 are preferred, and methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate are particularly preferred. These monomers are also preferably used in order to express the viscosity when the copolymer is melted.

When the proportion of the methyl methacrylate unit in the copolymer exceeds 99.5% by weight, the thermal decomposability due to depolymerization becomes large, while when it is less than 70% by weight, the heat resistance and weather resistance of the obtained foam are increased. Both of them are not preferable because they decrease. The acrylic copolymer in the present invention comprises 80 to 99% by weight of a methyl methacrylate monomer unit and 1 to 25% by weight of an alkyl acrylate monomer unit in which the alkyl group has 1 to 8 carbon atoms. Particularly preferred.

In the acrylic copolymer of the present invention, the most important conditions are the molecular weight and the molecular weight distribution. When the polymethylmethacrylate-converted weight average molecular weight and the polymethylmethacrylate-converted Z average molecular weight of the resin are used as the index, the viscosity at the time of melting is an indispensable factor for realizing fine and uniform foaming and obtaining a good foam, It became clear that the ductility can be controlled. Hereinafter, the polymethylmethacrylate-converted weight average molecular weight and the polymethylmethacrylate-converted Z average molecular weight are abbreviated as M _RW and M _RZ , respectively.

M _RW and M _RZ are obtained by carrying out the following measurements. That is, using tetrahydrofuran as a solvent,
Gel permeation chromatography (hereinafter abbreviated as GPC) was measured by using so-called monodisperse polymethylmethacrylate having a narrow molecular weight distribution as a standard substance of molecular weight,
Prepare a calibration curve of molecular weight and elution time. GPC is measured using a solution having a sample polymer concentration of 0.001 g / cm ³ and calculated based on the formulas (1) and (2) below. _{M RW = (ΣM Ri W I} ) / ΣW I (1) M RZ = {Σ (M Ri) 2 W I} / (ΣM Ri W I) (2) ( wherein, M _Ri and W _i, respectively i The polymethylmethacrylate-equivalent molecular weight of the second fraction and the polymer weight concentration of each fraction are represented, and Σ represents the total sum over all fractions.) Thus, the molecular weight measured by GPC is when the polymer contains a branched structure. Is generally an underestimated value without giving a true molecular weight, but is an effective index for comparison between resins in the present invention.

The acrylic copolymer of the present invention has an M _RW of 7
× 10 ⁴ to 50 × 10 ⁴ . 7 × 10 for M _RW
If it is less than ⁴ , the melt elasticity is low during foam molding, it is difficult to form fine and uniform cells, the appearance is inferior, and the mechanical strength of the resulting foam is lowered, which is not preferable. On the other hand, when M _RW exceeds 50 × 10 ⁴ , the viscosity at the time of melting becomes excessively high, which makes extrusion foaming particularly difficult, and when attempting to compensate for the insufficient melt viscosity by increasing the processing temperature, the thermal decomposition of the resin is accelerated. On the contrary, it is difficult to make the foam uniform, which is not preferable. From these viewpoints, M _RW is 8 × 10 ⁴ to 4
The range of 0 × 10 ⁴ is preferable, and 8 × 10 ^{4 to} 35 × 10
A range of ⁴ is especially preferred.

The acrylic copolymer of the present invention is M _RZ / M
It is necessary that the ratio of _RW is 1.7 to 5, and 1.8 to
It is preferably 5. Here, the ratio of M _RZ / M _RW represents the molecular weight distribution and is an index that can be related to the behavior of the resin during melting. When the ratio of M _RZ / M _RW is less than 1.7, the melt elasticity of the resin is insufficient, so that it is difficult to retain the bubbles during foaming and it is difficult to obtain a fine and uniform foam. In that case, it has been found that the elasticity at the time of melting is excessive and stable foam molding becomes difficult,
This was the most important point in completing the present invention.

The method for producing the acrylic copolymer of the present invention comprises:
Any method may be used as long as it is a method in which the molecular weight and the molecular weight distribution are controlled and a uniform polymer is obtained. For example, a method comprising the steps of conducting a polymerization reaction in parallel using a plurality of reactors and a step of uniformly mixing the polymers produced in each in a solution state or a melt state, via a plurality of series reactors The polymerization reaction is carried out continuously, and the molecular weight and molecular weight distribution of the polymer produced in each reactor are controlled to control the molecular weight and molecular weight distribution of the final polymer. How to combine,
There is a method of changing the molecular weight distribution of the produced polymer by adding a polymerization degree regulator and / or a monomer during the polymerization reaction.

Further, the acrylic copolymer of the present invention may be wholly or partly a branched polymer. The manufacturing method in this case is also not particularly limited. For example, a method in which an oligomer or polymer having a polymerizable functional group at one end (so-called macromer) is copolymerized with a monomer capable of being copolymerized therewith to form a graft polymer, or a backbone polymer is polymerized by a hydrogen abstraction reaction or the like. Method for creating a starting point and initiating polymerization of a monomer from this to produce a graft polymer Branched polymer using a polyfunctional initiator having three or more reactive groups capable of initiating polymerization in one molecule To produce a branched polymer using a polyfunctional chain transfer agent having three or more chain-transferable reactive groups in one molecule, an oligomer or polymer having a reactive group at one end There is a method in which a branched polymer is generated by an anionic polymerization method and then a coupling reaction is performed with a substance having three or more functional groups capable of reacting with the anionic polymerization method. .

In these methods, for example, the molecular weight of the polymerizable oligomer or polymer is controlled, and the molecular weight at the time of copolymerizing these with a monomer is also controlled by the use of a chain transfer agent or the like. Polymers with a molecular weight distribution can be produced. Furthermore, as a practical method for controlling the molecular weight and the molecular weight distribution widely, 2
Controlling the copolymerization rate of the bifunctional monomer and the molecular weight of the resulting copolymer when copolymerizing a bifunctional monomer having one polymerizable functional group with a normal monofunctional monomer There is a method of controlling the molecular weight distribution. This method is advantageous in that M _RW and M _RZ can be widely controlled by using only one reactor and that a polymer having a uniform dispersed state can be produced.

Examples of the bifunctional monomer include ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate,
1,4-butanediol dimethacrylate, polyethylene glycol diacrylate (CH ₂ CH ₂ O in the molecule
2 to 20 units), polyethylene glycol dimethacrylate (2 to 20 CH ₂ CH ₂ O units in the molecule)
and so on. These may be used alone or in combination of two or more. The copolymerization rate of the bifunctional monomer is generally determined by using a considerably small amount from the viewpoint of preventing the formation of a three-dimensional crosslinked product in order to make the obtained polymer soluble in a solvent during GPC measurement. Can be reached.

Further, the acrylic copolymer of the present invention may be a mixture of two or more kinds of branched polymers, and a branched polymer and an ordinary unbranched polymer (linear polymer) may be mixed and used. You may. Even with a polymer mixed in this way,
It is important that the ratio of Z-average molecular weight in terms of polymethylmethacrylate / weight average molecular weight in terms of polymethylmethacrylate is 1.7 to 5, and the molecular weight distribution should be set based on the measurement using gel permeation chromatography. You can

Further, the polymerization method for producing the acrylic copolymer of the present invention is not particularly limited, and a usual method capable of polymerizing a monomer mainly containing methyl methacrylate may be used. Generally, a radical polymerization method is used, but an anion polymerization method, a coordination polymerization method or the like may be used.
When it is carried out by a radical polymerization method which is usually carried out industrially, any method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method or an emulsion polymerization method may be used. here,
When a solvent is used at the time of polymerization, a chemically stable substance should be selected so as not to impair the color tone, weather resistance and light resistance of the acrylic copolymer produced. From this viewpoint, examples of the solvent include toluene, ethylbenzene, cyclohexane, cyclohexanone, butyl acetate and the like, and these can be used alone or in combination of two or more kinds.

The polymerization temperature for producing the acrylic copolymer of the present invention can be selected within an appropriate range depending on the polymerization method. In the radical polymerization method using an aqueous medium such as suspension polymerization or emulsion polymerization, it can be generally carried out at 50 to 120 ° C. In the continuous bulk polymerization method or continuous solution polymerization method using radical polymerization, the polymerization temperature is generally 100 ° C. or higher,
It is preferably carried out at 110 ° C. or higher. When producing a methacrylic resin with a high polymerization rate by a continuous bulk polymerization method or a continuous solution polymerization method, the reaction temperature is 100 ° C because the polymer alone or the solution consisting of the polymer, the monomer and the solvent has a high viscosity. If it is less than 1, it becomes difficult to continuously discharge from the reactor, which is not preferable.

As the polymerization initiator used in the production of the methacrylic resin of the present invention, when the radical polymerization method is used, any polymerization initiator generally used for radical polymerization can be used. For example, azo compounds such as azobisisobutyronitrile, azobisisovaleronitrile, 1,1-azobis (1-cyclohexanecarbonitrile), 2- (carbamoylazo) isobutyronitrile, di-
t-butyl peroxide, dilauroyl peroxide, t-butylperoxy-2-ethylhexanoate, 1,1-bis (t-butylperoxy) 3,3,5
There may be mentioned organic peroxides such as trimethylcyclohexane, cyclohexanone peroxide and 2,5-dimethyl-2,5-di (benzoylperoxy) hexane. These may be used alone or in combination of two or more. Further, these initiators are used in the range of 0.005 to 1% by weight based on the monomer mixture.

When the acrylic copolymer of the present invention is produced by a radical polymerization method, a chain transfer agent generally used in radical polymerization can be used to control the molecular weight. For example, mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, and 2-ethylhexyl thioglycolate are preferred. These chain transfer agents have M _RW of 7 × 10 ⁴ to 50 × when the acrylic copolymer of the present invention is measured by GPC.
It can be used by adding it to the monomer mixture at a concentration so as to be in the range of 10 ⁴ .

In the acrylic copolymer of the present invention, a release agent, a lubricant, an ultraviolet absorber, a heat stabilizer, an antioxidant, an electrification agent, which is usually used as necessary, is used as long as the effects of the present invention are not impaired. Inhibitors, light diffusers, dyes, pigments, etc. may be added. The method of blending these additives is not particularly limited, and a known method can be adopted. For example, a method of preliminarily dissolving an additive in a monomer mixture at the time of producing an acrylic copolymer, and polymerizing the additive, a melted state, a bead-shaped or pellet-shaped acrylic copolymer with the additive, etc. It is possible to cite, for example, a method of mixing at a desired ratio and kneading and pelletizing using an extruder.

The foam of the present invention is obtained by molding the above-mentioned acrylic copolymer by a usual foaming processing method to obtain a physical foam,
Any method of chemical foaming may be used. In terms of equipment, it can be produced by any of extrusion foam molding, injection foam molding, and bead foam molding. In particular, it is suitable for use in processing into a plate shape or a deformed shape by extrusion foam molding.

Examples of the foaming agent include saturated aliphatic hydrocarbons such as propane, butane and hexane, and halogenated hydrocarbons such as trichlorofluoromethane. These may be used alone or in combination of two or more. You may use it. In the present invention, a nucleating agent may be used during foam molding. A powder of talc or silica is preferably used as the nucleating agent.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto. The measurement in the examples and comparative examples was performed using the method described below or using a measuring instrument. (1) Composition analysis of acrylic copolymer A dichloromethane solution of a polymer is cast on a platinum boat.
Dry and pyrolyze in a nitrogen stream (PYR-2A made by Shimadzu)
Decomposes at 450 ℃ in the chamber, and immediately introduces the monomer component produced by depolymerization into the gas chromatography column.
analyzed. The results were obtained by quantitative calculation using the analysis result of the polymer of known composition obtained by bulk polymerization as a standard.

(2) Measurement of M _RW and M _{RZ Using} tetrahydrofuran as a solvent, a polymethyl methacrylate standard sample having a narrow molecular weight distribution (manufactured by Waters).
Gel permeation chromatography (abbreviated as GPC) of TOCOH HLC-8120
A TSK-gel-Super H type column manufactured by SOH was attached and measured to prepare a calibration curve of molecular weight and elution time. GPC is measured using a solution having a concentration of the sample polymer of 0.001 g / cm ³ and is calculated based on the formulas (1) and (2) below. _{M RW = (ΣM Ri W I} ) / ΣW I (1) M RZ = {Σ (M Ri) 2 W I} / (ΣM Ri W I) (2) ( wherein, M _Ri and W _i, respectively i The polymethyl methacrylate-equivalent molecular weight of the second fraction and the polymer weight concentration of each fraction are represented, and Σ represents the sum over all fractions).

(3) Drop Weight Strength A weight of 100 g was dropped from a height of 30 cm and the broken state of the foam plate was observed. (4) Evaluation of weather resistance The appearance and color tone after the foam was exposed for 1000 hours with a sunshine weatherometer were visually judged.

The abbreviations used in Examples and Comparative Examples indicate the following compounds. MMA; methyl methacrylate MA; methyl acrylate BA: butyl acrylate ST: styrene EGDMA: ethylene glycol dimethacrylate LPO; lauroyl peroxide n-OM; n-octyl mercaptan Furthermore, the following percentages and parts unless otherwise specified. Indicate weight% and parts by weight, respectively.

[0033]

【Example】

Example 1 In a stainless reactor having an internal volume of 60 liters, 30 liters of ion-exchanged water, 150 g of tricalcium phosphate,
Then, 1.2 g of sodium lauryl sulfate was added and dispersed, and the temperature was raised to 75 ° C. under stirring in a nitrogen atmosphere so that there was virtually no effect of oxygen. MMA18 800g,
MA 1200g, EGDMA 12g, LPO 40g, n
-OM 36 g and TINUVIN P (manufactured by Nippon Ciba Geigy) 2 g were added all at once, and the mixture was kept at 75 ° C for 3 hours to polymerize, then heated to 95 ° C and kept for 1 hour to carry out polymerization. It was completed. The reaction product was filtered, washed with water, and dried to obtain a bead-shaped acrylic copolymer (A).

GPC analysis of this methacrylic resin (A) gave the results of M _RW = 23 × 10 ⁴ and M _RZ / M _RW = 2.4. In addition, when the composition was analyzed using a pyrolysis gas chromatography method, MMA unit / MA unit = 94/6 (weight ratio)
Was obtained. Next, talc was mixed with the methacrylic resin (A) as a foaming nucleating agent with a Henschel mixer, and an extrusion foaming device with a screw diameter of 30 mm was used. 1
A low foam plate having a size of 5 cm and a density of about 0.1 to 0.2 g / cm ³ was foam-molded. The evaluation results are shown in Table 1.

Example 2 MMA18200g, MA1800g, EGDMA24
g, LPO 40 g, n-OM 52 g, and tinuvin P
Polymerization was carried out in the same manner as in Example 1 except that a monomer mixture consisting of 2 g (manufactured by Nippon Ciba Geigy) was used to obtain an acrylic copolymer (B). GPC analysis of this acrylic copolymer (B) revealed that M _RW = 27 × 10 ⁴ ,
A result of M _RZ / M _RW = 2.8 was obtained. When the composition of the product was analyzed by the pyrolysis gas chromatography method, the result of MMA unit / MA unit = 91/9 (weight ratio) was obtained. The acrylic copolymer (B) was molded into the same extruded foam plate as in Example 1. The evaluation results are shown in Table 1.

Example 3 50 parts by weight of the acrylic copolymer (B) prepared in Example 2, M _RW = 14 × 10 ⁴ , M _RZ / M _RW = 1.5, MM
50 parts by weight of a normal acrylic copolymer (C) having A unit / MA unit = 94/6 (weight ratio) was mixed with talc in a Henschel mixer, and extrusion foam molding was carried out in the same manner as in Example 1. GPC analysis of this molded product showed that it was M _RW
= 21 × 10 ⁴ , M _RZ / M _RW = 2.8. The evaluation results of the foamed molded product are shown in Table 1.

Example 4 Extrusion foam molding was carried out in the same manner as in Example 3 except that 20 parts by weight of the acrylic copolymer (B) and 80 parts by weight of the acrylic copolymer (C) were mixed with talc. A GPC analysis of this molded body revealed that M _RW = 17 × 10 ⁴ , M
The result of _RZ / M _RW = 2.3 was obtained. The evaluation results of the foamed molded product are shown in Table 1.

Example 5 5 parts by weight of the acrylic copolymer (B) and 95 parts by weight of the acrylic copolymer (C) were mixed with talc,
Extrusion foam molding was performed in the same manner as in Example 3. GP of this molded product
When C analysis was carried out, M _RW = 15 × 10 ⁴ , M _RZ /
A result of M _RW = 1.8 was obtained. The evaluation results of the foamed molded product are shown in Table 1.

Example 6 A monomer mixture consisting of 94 parts by weight of MMA, 6 parts by weight of MA, 0.02 parts by weight of azobisisovaleronitrile, and 0.01 parts by weight of tinuvin P was stirred in a stainless steel reactor equipped with a stirrer. Warm to 50 ° C for 1 hour and M _RW = 1
About 10% of a polymer of 40 × 10 ⁴ , M _RZ / M _RW = 1.6
A syrup containing was prepared. In addition to this syrup
0.18 parts by weight of M was melted, poured into a glass cell with a gasket, and kept in a hot water bath at 50 ° C. for about 15 hours. Then, the glass cell was heated in an oven at 130 ° C. for 2 hours to complete the polymerization. The obtained cast plate is referred to as an acrylic copolymer (D). When this is analyzed, M _RW = 2
The results were 7 × 10 ⁴ , M _RZ / M _RW = 4.5, and MMA unit / MA unit = 94/6 (weight ratio). This cast plate was crushed to produce an extruded foam plate in the same manner as in Example 1. The evaluation results are shown in Table 1.

Example 7 18000 g of MMA, 2000 g of MA, EGDMA24
g, LPO 40 g, n-OM 100 g, and TINUVIN P (manufactured by Nippon Ciba Geigy) were used in the same manner as in Example 1 except that a monomer mixture was used to obtain an acrylic copolymer (E). . When this was subjected to GPC analysis, the results of M _RW = 8 × 10 ⁴ and M _RZ / M _RW = 2.7 were obtained. When the composition of the product was analyzed by the pyrolysis gas chromatography method, the result of MMA unit / MA unit = 90/10 (weight ratio) was obtained. The acrylic copolymer (E) was molded into the same extruded foam plate as in Example 1. The evaluation results are shown in Table 1.

Example 8 MMA18 800 g, MA 1200 g, EGDMA24
g, LPO55g, n-OM14g, and tinuvin P
Polymerization was carried out in the same manner as in Example 1 except that a monomer mixture consisting of 2 g (manufactured by Nippon Ciba Geigy) was used to obtain an acrylic copolymer (F). When this was subjected to GPC analysis, the results of M _RW = 31 × 10 ⁴ and M _RZ / M _RW = 28 were obtained. When the composition of the product was analyzed by the pyrolysis gas chromatography method, the result of MMA unit / MA unit = 94/6 (weight ratio) was obtained. The acrylic copolymer (F) was molded into the same extruded foam plate as in Example 1. The evaluation results are shown in Table 2.

Example 9 MMA 16000 g, BA 4000 g, EGDMA24
g, LPO 45 g, n-OM 50 g, and tinuvin P
Polymerization was carried out in the same manner as in Example 1 except that a monomer mixture consisting of 2 g (manufactured by Nippon Ciba Geigy) was used to obtain an acrylic copolymer (G). GPC analysis of this acrylic copolymer (G) revealed that M _RW = 28 × 10 ⁴ ,
A result of M _RZ / M _RW = 2.8 was obtained. When the composition of the product was analyzed by the pyrolysis gas chromatography method, the result of MMA unit / BA unit = 80/20 (weight ratio) was obtained. The acrylic copolymer (G) was molded into the same extruded foam plate as in Example 1.
The evaluation results are shown in Table 2.

Comparative Example 1 The acrylic copolymer (C) was extrusion foamed and evaluated in the same manner as in Example 1. The obtained foam plate was not uniform in foaming and was brittle as a whole. The results are shown in Table 2.

Comparative Example 2 Except that 2 parts by weight of the acrylic copolymer (B) and 98 parts by weight of the acrylic copolymer (C) were mixed with talc,
Extrusion foam molding was performed in the same manner as in Example 3. GP of this molded product
When C analysis was carried out, M _RW = 15 × 10 ⁴ , M _RZ /
A result of M _RW = 1.6 was obtained. The evaluation results of the foamed molded product are shown in Table 2.

Comparative Example 3 Talc was used as a standard acrylic copolymer (H) having M _RW = 18 × 10 ⁴ , M _RZ / M _RW = 1.5, MMA unit / MA unit = 94/6 (weight ratio). The mixture was mixed with a Henschel mixer and extrusion foamed in the same manner as in Example 1. The evaluation results are shown in Table 2.

COMPARATIVE EXAMPLE 4 The composition of MMA unit / ST unit = 60/40 (weight ratio) and the MS resin of M _RW = 14 × 10 ⁴ and M _RZ / M _RW = 1.6 were used. Similarly, extrusion foam molding was performed and evaluated. The obtained foam board had poor weather resistance. The evaluation results are shown in Table 2.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

The resin foam of the present invention has a density of 0.014.
So-called high foam ~0.074g / cm ³ can also be produced any of so-called low foam density 0.075~0.93g / cm ^3. The high foam is suitable as a heat insulating material and a cushioning material by utilizing its mechanical strength, and is also advantageous in that it emits less smoke when incinerated and discarded.
Further, since the low-foamed material makes good use of weather resistance and mechanical strength and can be subjected to processing such as nailing and sawing, it can be widely used as synthetic wood for outdoor use, soundproofing material, and signboard.

Claims (1)

[Claims] 1. A methyl methacrylate monomer unit 70-
99.5% by weight and other copolymerizable monomer units of 0.
5 to 30% by weight, the polymethylmethacrylate-converted weight average molecular weight measured by gel permeation chromatography is 7 × 10 ⁴ to 50 × 10 ⁴ , and the polymethylmethacrylate-converted Z average molecular weight / polymethylmethacrylate. The ratio of equivalent weight average molecular weight is 1.7
The resin foam which consists of an acrylic copolymer which is ~ 5.