JPH037696B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel resin foam. More specifically, the present invention relates to a resin foam having excellent weather resistance, oil resistance, solvent resistance, impact resistance, and post-processability. Conventionally, resin foams made of polystyrene, impact-resistant polystyrene, styrene-acrylonitrile resin, acrylonitrile-butadiene-styrene resin, etc. are known. However, such resins mainly composed of styrene have poor weather resistance and cannot be used outdoors, and also have the disadvantage that they tend to crack when they come into contact with vegetable oils and the like. Furthermore, although styrene-acrylonitrile resin foam has relatively good oil resistance,
Thermal decomposition may occur during foam molding at high temperatures.
This has the disadvantage that cell size, color tone, etc. change, making quality control difficult. Furthermore, the gas efficiency of the foaming agent is low, so a penetrating foaming agent cannot be used, and the resulting resin foam is brittle, making post-processing difficult, and there are many problems in practical use. On the other hand, polymethyl methacrylate is known as a resin that compensates for various drawbacks of polystyrene, but
This has the disadvantage that when used alone, it is difficult to form a foam, especially a highly foamed product. The reason for this is not yet completely understood, but the viscosity of the resin is high when melted, and lowering the molecular weight to lower the melt viscosity reduces strength and solvent resistance. Possible reasons include that it is difficult to disperse and permeate homogeneously, that thermal decomposition easily occurs during the hot melting process up to foaming, and that it is difficult to control the foaming rate. The present inventors have previously proposed a resin foam that compensates for these drawbacks. (Special application 1973-
No. 121658) Although the resin foams proposed earlier have various advantages, they are somewhat unsatisfactory in impact resistance, especially in highly foamed materials, and have the disadvantage of being easily shattered by impact. It also had the disadvantage of being easily attacked by certain solvents. The present inventors have completed the present invention as a result of intensive research to improve these drawbacks. That is, the present invention comprises 40 to 60% by weight of methyl methacrylate and styrene.
Composed of 60~40% by weight, solution viscosity index 0.07~
0.20, copolymer with residual monomer content of 0.6% by weight or less
20-90 parts by weight and 80 parts by weight of multilayer polymer containing elastic material
~10 parts by weight of a resin foam, in which a multilayer structure polymer containing an elastic body is a hard layer (first layer).
Consists of a basic structure of soft layer (second layer) - hard layer (third layer), or has one or more intermediate layers between the first layer and the second layer or between the second layer and the third layer. (1) The hard first layer is a monomer selected from the group consisting of methyl methacrylate, styrene, and mixtures thereof, or is copolymerizable with not more than 20% by weight of these monomers. (2) The hard second layer is the first layer or the first layer and the second layer.
In the presence of an intermediate layer between the layers, 55 to 100% by weight of at least one selected from butadiene, substituted butadiene, and alkyl acrylate whose alkyl group has 1 to 8 carbon atoms, together with up to 40% by weight of these. Comprising a polymerizable monofunctional monomer, 5% by weight or less of a monofunctional crosslinking agent, and 5% by weight or less of a polyfunctional grafting agent, the polymerizable polymer when polymerized in the absence of the first layer or this and an intermediate layer. It is an elastic body formed by polymerizing a monomer mixture with a combined Tg of 25°C or less. (3) The hard third layer is the second layer or an intermediate layer between the second layer and the third layer. a monomer selected from the group consisting of methyl methacrylate, styrene and mixtures thereof, or a monomer copolymerizable with these in an amount of not more than 20% by weight;
This resin foam is a polymer obtained by polymerizing a monomer mixture and has a Tg of 25° C. or higher when polymerized in the absence of a layer or an intermediate layer. In the copolymer used in the present invention, the ratio of methyl methacrylate and styrene is 40 to 60% by weight and 60 to 40% by weight of styrene, based on the desired weather resistance, oil resistance, foaming processability, and post-processability. It is necessary to choose within the range of. If the amount of methyl methacrylate is more than this range, the foaming processability will be poor, and if it is less than this range, the weather resistance and oil resistance will be poor. For example, it tends to turn yellow due to accelerated exposure with a sunshine weather meter, and it tends to crack when it comes into contact with margarine, salad oil, etc. The copolymer used in the present invention needs to have a solution viscosity index in the range of 0.07 to 0.20. This is because, especially in the case of extrusion foaming, when it is less than 0.07, the melt viscosity of the system is too low, making it difficult to obtain an appropriate expansion ratio and reducing the closed cell ratio. Moreover, the mechanical strength of the obtained foam is reduced, making it impractical. Conversely, if it is larger than 0.20, the melt viscosity of the system will increase and foaming will become difficult, and if the temperature is raised to lower the melt viscosity, the solubility of the blowing agent in the resin will decrease and a good foam will not be obtained. It is from. In the case of low foaming by injection, a wider range of conditions can be selected than in the case of high foaming by extrusion, but a solution viscosity index within the above range often gives good results. Furthermore, the smaller the amount of residual monomer in the copolymer, the better the mechanical properties and thermal properties will be. In the present invention, the amount of residual monomer is 0.6% by weight or less, preferably 0.3% by weight or less. residual monomer
When the amount exceeds 0.6% by weight, the heat deformation resistance decreases rapidly.
Poor foaming processability. The copolymer used in the present invention is produced by combining methyl methacrylate and styrene into a powder by a generally known polymerization method such as emulsion polymerization, suspension polymerization, or bulk polymerization.
Obtained in the form of beads or pellets. In particular, copolymers with a small amount of residual monomer and no cyanide decomposition products can be prepared by using tert-butyl peroxy esters, such as tert-butyl peroxy isobutyrate, tert-butyl peroxy pivalate, as an initiator. Such as tert-butyl peroxy-2-ethylhexanoate can be easily obtained by using a linear alkyl mercaptan such as n-octyl mercaptan, n-dodecyl mercaptan, etc. as a chain transfer agent. The multilayer structure polymer containing an elastic body used in the present invention is disclosed in Japanese Patent Application No. 109811/1983 (Japanese Patent Application No. 55233/1983),
Japanese Patent Application No. 51-133474 (Japanese Unexamined Patent Application No. 53-58554), Japanese Patent Application No. 162494-1984 (Unexamined Japanese Patent Application No. 57-85843), Japanese Patent Application No. 56
−67684 (Japanese Unexamined Patent Publication No. 182310, 1983), Patent Application No. 182310
No. 84306 (Japanese Unexamined Patent Publication No. 1983-200411) and patent application No. 1983-
No. 84307 (Japanese Unexamined Patent Publication No. 57-200412) A multilayer containing an elastic body with a basic structure of hard layer (first layer) - soft layer (second layer) - hard layer (third layer) described in each publication. It is a structural polymer and is produced in powder form by a well-known emulsion polymerization method. This multilayer structure polymer exhibits excellent solvent resistance when the particle size is small, and particularly when the particle size is 200 to 900 Å, the solvent resistance effect is remarkable. In addition, the first layer may contain a monomer selected from methyl methacrylate, styrene, or a mixture thereof, or a monomer copolymerizable with these in an amount of 20% by weight or less, such as methyl acrylate, ethyl acrylate, or acrylic. a second hard layer, which is a polymer having a Tg of 25° C. or higher obtained by polymerizing a mixture of butyl acid, ethyl methacrylate, propyl methacrylate, substituted styrene, a nitrile unsaturated compound, acrylonitrile, methacrylonitrile, and vinyl complex acid; In the presence of the first layer, the layer contains butadiene, substituted butadiene, and an alkyl group having 1 to 1 carbon atoms.
55 to 100% by weight of at least one selected from 8 acrylic esters, such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and i-butyl acrylate;
40% by weight or less of monofunctional monomers copolymerizable with these, such as alkyl methacrylates, styrene, nitrile unsaturated compounds, and 5% by weight or less of polyfunctional crosslinking agents, such as ethylene glycol dimethacrylate, ethylene glycol diacrylate, Propylene glycol diacrylate, butylene glycol diacrylate, polyethylene glycol diacrylate, divinylbenzene, trivinylbenzene, and up to 15% by weight of a polyfunctional grafting agent such as allyl unsaturated carboxylic acid, metallyl esters, allyl acrylate, methacrylic acid The soft layer is made of a monomer mixture consisting of allyl, diallyl maleate, etc., and has a Tg of 25°C or less when polymerized in the absence of the first layer, and the third layer is the second layer.
In the presence of the layer, a monomer selected from methyl methacrylate, styrene or a mixture thereof, or a monomer copolymerizable with these in an amount of up to 20% by weight (compared to the monomer used in the first layer). Tg when polymerized in the absence of the second layer
A hard layer formed by polymerizing a monomer mixture whose temperature is 25°C or higher, a three-layer multilayer structure polymer, or a hard layer formed by polymerizing a monomer mixture whose hard layer (first layer) - soft layer (second layer)
Layer) - A multilayer structure having a basic structure of a hard layer (third layer) and one or more intermediate layers provided between the first layer and the second layer or between the second layer and the third layer. The polymer is preferable because it has excellent impact whitening resistance and boiling water whitening resistance, and in particular, the outermost hard layer of the multilayer structure polymer has a structure with a molecular weight gradient in which the molecular weight decreases from the inside to the outside. In some cases, it has even more favorable effects. The resin foam of the present invention comprises the above-mentioned copolymer 20 to 90
There are cases in which 80 to 10 parts by weight of a multilayer structure polymer containing parts by weight and elastic material are kneaded and granulated and then foamed, and cases in which each raw material is blended and then made into a foam at once with a blowing agent, a nucleating agent, etc. There are, and each can be used depending on the purpose. In the present invention, if the content of the multilayer polymer containing an elastic body is more than the above range, the foaming processability will be poor, and if it is less than the above range, no improvement in impact resistance or solvent resistance can be expected. For foaming, both physical foaming and chemical foaming methods are used depending on the type of foaming agent. Moreover, in terms of equipment, it is possible to manufacture by any of extrusion foam molding, injection foam molding, and bead foam molding. In particular, it is advantageous to process the material into a plate shape or irregular shape by extrusion foam molding. The resin foam of the present invention has a density of 0.014 to 0.056 g/cm ³
The so-called high foam material with a density of 0.075 to 0.93 g/cm ³
It is possible to produce any of the so-called low foam products. Highly foamed materials are ideal for insulation and cushioning materials due to their weather resistance and resistance to breakage.Additionally, they also have the secondary effect of being easy to incinerate as they emit little smoke after use. be. In addition, low-foam materials have excellent weather resistance and impact resistance, making them ideal for use outdoors as synthetic wood, hard insulation materials, soundproofing materials, and outdoor signboards. Furthermore, due to its impact resistance, saw cutting,
It is easy to process such as nailing and has a wide range of uses. In the resin foam of the present invention, materials commonly used in the production of foam, such as ultraviolet absorbers, antioxidants, dyes and pigments, antistatic agents, etc., may be added depending on the purpose. It can be added as long as it does not impair the physical properties of the body. Next, the present invention will be explained in more detail with reference to Examples. The solution viscosity index (ηsp/c), amount of residual monomer, and particle size in Examples are measured as follows. [Solution viscosity index] Approximately 130 mg of resin is dissolved in 50 ml of chloroform.
Measured with an Ostwald viscometer at 25°C and calculated using the following formula. ηsp/c={(t/to)-1}/c t: Time required for solution to fall to: Time required for only chloroform to fall c: Polymer concentration (g/) [Residual monomer amount] Hydrogen flame detection gas chromatography It was measured using the internal standard method under the following conditions. Column packing material: Carbowax Column temperature: 120°C Carrier gas: Nitrogen [Particle size] Measured using an electron microscope. Example 1 [Production of copolymer] A monomer mixture of 50 parts by weight of methyl methacrylate and 50 parts by weight of styrene was mixed with 0.36 parts by weight of tert-butyl peroxyisobutyrate and n-dodecyl mercaptan.
Suspension polymerization was carried out in a 0.5% aqueous solution of sodium polyacrylate to which 0.15 parts by weight was added. Polymerization was carried out at 80°C, and after the exothermic peak, curing was carried out at 100°C to complete the polymerization. By separating the reaction product, washing and drying, bead-shaped resin was obtained. This resin had a ηsp/c of 0.12, and residual monomers were 0.04% by weight of methyl methacrylate and 0.04% by weight of styrene. [Manufacture of multilayer structure polymer] Emulsifier dioctyl sodium sulfosuccinate
First, a uniform mixture of 10 parts by weight of methyl methacrylate, 10 parts by weight of styrene, and 0.02 parts by weight of diisopropylbenzene hydroperoxide was added to a 0.4% aqueous solution as the first layer, 0.1 part by weight of Rongarit was added, and the mixture was heated at 80°C for 20 minutes. After polymerization for 1 minute, a homogeneous solution of 150 parts by weight of butyl acrylate, 1.0 part by weight of allyl methacrylate, and 0.15 parts by weight of diisopropylbenzene hydroperoxide was added dropwise over 1 hour to react. After reacting for 1 hour after completion of the dropwise addition, a homogeneous solution of 15 parts by weight of methyl methacrylate, 15 parts by weight of styrene, 0.03 parts by weight of diisopropylbenzene hydroperoxide, and 0.1 parts by weight of n-octyl mercaptan was added as the third layer, and the mixture was reacted for 30 minutes. After that, the temperature was raised to 95°C and the reaction was carried out for 1 hour. The particle size of the obtained polymer was 1200 Å. This reaction product was salted out with an aqueous aluminum chloride solution to separate the polymer component, washed and dried to obtain a white powdery resin. [Manufacture of resin foam] Copolymer beads and multilayer structure polymer powder were mixed in varying amounts using a Henschel mixer, and using a 30 mm extrusion foaming device, Freon was used as a foaming agent and talc was used as a nucleating agent. A low foam board with a density of 0.11 (g/cm ³ ) was foam-molded. The results are shown in Table-1.

[Table] Unchanged: Excellent Deformation: Good Destruction: Bad Example 2 A copolymer was prepared in the same manner as in Example 1 except that the ratio of methyl methacrylate and styrene in the copolymer was changed.
A foam board containing 50 parts by weight and 50 parts by weight of the multilayer structure polymer was obtained. The results are shown in Table-2.

[Table] Example 3 Multilayer structure polymer obtained by changing the amount of emulsifier and changing the particle size of the polymer during production of multilayer structure polymer
A foam board was obtained in the same manner as in Example 1 using 20 parts by weight of the copolymer and 80 parts by weight of a copolymer consisting of 50% by weight of methyl methacrylate and 50% by weight of styrene. The results are shown in Table-3.

[Table] *5 Condition after being immersed in gasoline for 5 minutes and left at room temperature for 1 day.
No change: Excellent Almost no change: Good Cracks: Bad Example 4 The multilayer structure polymer was the same as Example 1 up to the second layer, and the third layer was 7.5 parts by weight of methyl methacrylate and 7.5 parts by weight of styrene. A homogeneous solution of 0.015 parts by weight of diisopropylbenzene hydroperoxide was added and polymerized for 30 minutes, and then 0.05 parts by weight of n-octyl mercaptan was added to the same monomer mixture as for the third layer and polymerized for 30 minutes. A four-layer structure polymer was obtained by processing in the same manner as in Example 1. A foam was obtained in the same manner as in Example 1 by mixing this and the copolymer beads of Example 1 in an amount of 50 parts by weight. When this foam was measured for falling weight impact in the same manner as in Example 1, it did not whiten at all due to falling weights, and when it was immersed in boiling water for 30 minutes, it did not whiten at all.

Claims (1)

[Claims] 1. Consists of 40 to 60% by weight of methyl methacrylate and 60 to 40% by weight of styrene, and has a solution viscosity index of 0.07.
~0.20, 20 to 90 parts by weight of a copolymer with a residual monomer content of 0.6% by weight or less, and a multilayer structure polymer containing an elastic body.
The hard layer (first layer) is a resin foam consisting of 80 to 10 parts by weight, and a multilayer structure polymer including an elastic body.
- Consists of the basic structure of - soft layer (second layer) - hard layer (third layer), or between the first layer and the second layer,
(1) The hard first layer is made of a monomer selected from the group consisting of methyl methacrylate, styrene, and mixtures thereof. (2) The soft second layer is made of a polymer having a Tg of 25°C or higher, which is obtained by polymerizing a mixture of these and a monomer copolymerizable with these in an amount of 20% by weight or less. In the presence of the first layer or an intermediate layer between the first layer and the second layer, at least one member selected from butadiene, substituted butadiene, and alkyl acrylates whose alkyl group has 1 to 8 carbon atoms is added. 100% by weight, 40% by weight or less of a monofunctional monomer copolymerizable with these, 5% by weight or less of a polyfunctional crosslinking agent, and 5% by weight or less of a polyfunctional grafting agent; It is an elastic body formed by polymerizing a monomer mixture, and the Tg of the polymer when polymerized in the absence of a layer is 25°C or less, (3) The hard third layer is the second layer or this. and in the presence of an intermediate layer between the second layer and the third layer, a monomer selected from the group consisting of methyl methacrylate, styrene and mixtures thereof, or copolymerizable with these in an amount of up to 20% by weight. A resin foam, which is a polymer obtained by polymerizing a monomer mixture, and has a Tg of 25° C. or higher when polymerized in the absence of a second layer or an intermediate layer. 2. The resin foam according to claim 1, wherein the molecular weight of the outermost layer of the multilayer structure polymer containing an elastic body decreases from the inside to the outside. 3. The resin foam according to claim 1, wherein the multilayer structure polymer containing an elastic body has a particle size of 200 to 900 Å. 4. The resin foam according to claim 1, wherein the copolymer is obtained by using tert-butyl peroxy esters as an initiator and linear alkyl mercaptans as a chain transfer agent.