JPH0445333B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a foam having uniform and fine foam cells and having excellent rigidity. More specifically, the present invention provides a composite structure in which a microfoamed part of an amorphous thermoplastic resin is formed into an island, and a sea part surrounding the island is made up of a continuous thin layer part of a crystalline thermoplastic resin that is not substantially foamed. This invention relates to a composite foam with excellent physical properties. Furthermore, in order to manufacture the foam, the present invention comprises an amorphous thermoplastic resin and a crystalline thermoplastic resin that are relatively difficult to dissolve in each other, the latter resin forming the sea part and the former resin forming the island part. The present invention provides a novel method comprising foaming mainly the island portions of a composition having a sea/island structure. BACKGROUND ART Many foams made of various resins have been known and are widely used in various fields. In particular, the main resins used for the foam include polystyrene resins, polyvinyl chloride resins, polyolefin resins (especially polyethylene), polyurethane resins, and various rubbers. Although each resin is used for applications that take advantage of its characteristics,
Each of these methods has its own drawbacks, which naturally limits its scope of use and leaves behind various problems. For example, polystyrene resin foam has good foaming characteristics, so it can be obtained relatively easily by various methods, and the resulting foam has high rigidity and excellent heat insulation properties, but it has poor heat resistance. chemical resistance,
There are problems with tensile properties, etc. On the other hand, polyolefin resin foams have excellent heat resistance, chemical resistance, tensile properties, and hygroscopicity, but have problems with rigidity and dimensional stability. In addition, because it is crystalline, the viscosity changes rapidly with temperature, and the foam molding conditions are narrower.It is difficult to obtain a highly foamed product without crosslinking. ing. In particular, polypropylene resins have problems in molding, such as a narrow molding temperature range and failure to form uniformly fine cells, and the reality is that little progress has been made in practical use of polypropylene resins. Conventionally, various studies have been conducted to solve these problems from the viewpoint of both materials and molding techniques. Foams made from mixtures of various resins have been considered for improvements in materials. Most of these foams are mainly combinations of polyolefin and polystyrene, polyolefins, or rubber. Although these foams are partially effective in improving dimensional stability and forming uniform, fine cells, the overall physical properties and foaming characteristics of the foams are intermediate between the properties of each constituent resin. However, it was not possible to expect a significant improvement in quality. In particular, when foaming a mixture of crystalline resin and amorphous resin, the properties of the amorphous resin, which has relatively good foaming properties, are not utilized, and the current situation is that the foaming properties are only comparable to those of the crystalline resin alone. It is. Foams made by mixing a foaming agent with a mixture of resin and inorganic and organic fillers are already known, but
Usually, by mixing fillers, the film forming properties during foaming deteriorate and the dissipation of generated gas becomes significant.
A highly foamed product could not be obtained, and the foamed product obtained had coarse cells and a poor appearance. In addition, at present, the reinforcing effect of fillers has not yet been sufficiently exerted. Therefore, the inventors of the present invention have conducted intensive research in order to fully express the characteristics of various resins, particularly in order to improve both the foaming characteristics and the physical properties of the foam. As a result, in the combination of amorphous thermoplastic resin and crystalline thermoplastic resin, which are relatively difficult to dissolve in each other, by selectively foaming the islands, the characteristics of each resin constituting the sea and islands can be improved. In particular, by using amorphous thermoplastic resin with good foaming properties for the resin that makes up the islands, the foam molding conditions are wide, and the cells are uniform and fine, forming a sea. It has been discovered that a composite foam that also has the properties of a crystalline thermoplastic resin can be obtained. Furthermore, we have discovered that by mixing inorganic and organic fillers with the resin that makes up the sea, the reinforcing effect of the filler can be effectively expressed without deteriorating the foaming properties, leading to the present invention. Conventional composite foam sheets made of two or more types of resin are foamed in both phases, regardless of the sea or island, so the foaming characteristics of the two phases are different, resulting in coarse cells and dissipation of generated gas. is significant, and the foaming ratio cannot be increased. Especially when the sea is a crystalline resin, even if you mix an amorphous resin with good foaming properties,
Since most of the foaming occurs in the crystalline resin phase, no improvement in foaming properties is observed. Therefore, in the present invention, a chemical and/or physical foaming agent is mixed in advance with the amorphous thermoplastic resin constituting the islands, and the islands are mainly foamed using various foaming methods. Even when resins are mixed, it is possible to obtain a foam having uniform, fine cells if conditions are selected. Furthermore, when a resin with good foaming properties is used as the material that makes up the islands, the foaming properties of the entire foam are mostly determined by the material that makes up the islands. This makes it possible to form a uniform and fine foam. Usually, in an incompatible resin mixture, the interface between the sea and the island is a weak part. In general foams, air bubbles are also generated at this interface, so the strength (especially tensile strength) of the resulting foam
In contrast, in the composite foam according to the present invention, almost no air bubbles are generated at the sea-island interface, so it has higher strength than the conventional composite foam. For composite foams containing inorganic and/or organic fillers, it is important to note that in the case of conventional composite foams, the mixing of fillers deteriorates the film-forming properties of the material and increases the dissipation of blowing agent gas. The foam became coarse, the expansion ratio did not increase, and the foam surface became uneven, making it impossible to obtain a satisfactory foam. On the other hand,
Since the composite foam according to the present invention contains almost no filler in the foaming islands, the foaming properties are almost the same as those of ordinary foams that do not contain fillers, and a wide range of foam molding conditions can be used to obtain a good foam. can get. Furthermore, in conventional foams, bubbles tend to form at the interface between the resin and the filler, which greatly reduces the reinforcing effect of the foam by the filler. Since there are few bubbles generated at the interface with the filler, a sufficient reinforcing effect by the filler is exerted, and a highly rigid foam can be obtained. Ideally, the foam exhibits a sufficient reinforcing effect by having a filler skeleton in which the filler is completely embedded in the non-foamed phase existing around the cells. The present invention will be explained in more detail below. The foam according to the present invention consists of a sea of crystalline thermoplastic resin and an island of amorphous thermoplastic resin, but the resins constituting each phase can be any resin as long as it is a combination of moderately incompatible resins. It doesn't matter if it's a combination. A completely compatible combination is not suitable because it will not form a sea-island structure. As a specific guideline, the absolute value (ΔSP value) of the difference between the solubility parameters of each constituent resin can also be defined to some extent. The ΔSP value in this application is also shown as a calculated value using the Small method. (Reference, PASmall, J.
Appl.Chem. 3 , 71 (1953) Usually, a combination of resins with a ΔSP value of approximately 0.5 or more and 4 or less is considered appropriate in terms of practical quality. When the ΔSP value is less than 0.5, the compatibility of each resin becomes very good, and the structure of the sea and islands becomes unclear, and the dispersion unit of the islands becomes too small. In addition, if the ΔSP value exceeds 4, the compatibility of each resin may deteriorate extremely and the basic physical properties of the foam may deteriorate.
Depending on the use of the foam, it may be acceptable even if the ΔSP value is 4 or more and the foam is completely incompatible. However, the sea/island structure of a composite made of a mixture of different resins cannot be clearly defined solely by the compatibility of each resin, but is greatly influenced by the composition, melt viscosity, and mixing temperature of each resin. Although it is not possible to specify a combination of resins based on the ΔSP value alone, it is useful as a guide for resin selection. Basically, the crystalline thermoplastic resin that makes up the sea can be any resin as long as it can realize an appropriate sea/island structure, but preferably it can be any resin that makes up the islands. Unless the resin has properties that complement the properties, there will be little practical effect.
For example, high density, medium density, low density polyethylene,
These include polyolefin resins such as polypropylene and copolymers of these and α-olefins, polyamide resins, and polyester resins. The amorphous thermoplastic resin constituting the islands may be any amorphous thermoplastic resin, but preferably a resin with good foaming properties. In other words, materials that do not have a rapid viscosity change with temperature and have a large gas retention capacity during melting are preferred; specifically, polystyrene-based, polyvinyl chloride-based, acrylate-based,
Methacrylate, polycarbonate, ABS
type, AS type resin, etc. The composition of each resin constituting the sea and islands is such that the resin constituting the sea is 95 to 30 wt%, preferably 90 to 60 wt%, and the resin constituting the island is 5 to 70 wt%, preferably 10 to 40 wt%. The resin that makes up the island is 5wt%
If the amount is less, the foaming ratio of the island will become relatively too high to obtain the same foaming ratio, or the foaming will extend to the sea, making it impossible to obtain the desired foamed structure. In addition, when it is over 70%, it is normal sea.
It is difficult to form an island structure, and the foamed structure aimed at by the present invention cannot be achieved. The sea and island resins used in the present invention may contain additives normally included in resins, such as antioxidants, slip agents, and AS agents. In the present invention, the inclusion of an inorganic and/or organic filler in the sea can be expected to have a significant improvement effect, especially compared to conventional foams. The fillers used are commonly used fillers and are not particularly limited, but include, for example, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, aluminum phosphate, talc, mica, clay, These include inorganic fillers such as carbon black, white carbon, and zeolite, and organic fillers such as phenol resin powder and ebonite powder. When inorganic and/or organic fillers are added to the sea, 5 to 80wt is added to the resin that makes up the sea.
%, preferably 10 to 60 wt%. If the amount of the filler is less than 5 wt%, the effect of adding the filler cannot be expected to be significant, and if it exceeds 80 wt%, the film forming properties during foam molding will deteriorate, making it impossible to obtain a good foam. The blowing agent used in the present invention is not particularly limited, but it is preferable that the blowing agent itself has more interaction (solubility) with islands than with the sea, or generates a gas that is more easily dissolved in islands. Even better if it's something. Examples of the blowing agent used in the present invention include azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, N,
N'-dinitrosopentamethylenetetramine, N,
Chemical blowing agents such as N'-dimethyl-N,N'-dinitroterephthalamide, benzenesulfonylhydrazide, p-toluenesulfonylhydrazide, p,p'-oxybisbenzenesulfonylhydrazide, carbonates, or propane, butane, pentane,
These are physical blowing agents such as dichlorodifluoromethane, dichloromonofluoromethane, trichloromonofluoromethane, methanol, and ethanol. These blowing agents can be appropriately selected and used depending on the combination of resins used, and are commonly used. Of course, a foaming aid and a nucleating agent may also be used together. In the present invention, before mixing the resin forming the sea and the resin forming the islands, it is necessary to mix the foaming agent with the resin forming the islands in advance. The mixing method may be an extruder, a Banbury mixer, a calender roll, etc., or an appropriate method such as mixing or impregnating a physical blowing agent in the form of a liquid or a gas at normal temperature and normal pressure using a conventional method. Foaming methods include extrusion foaming, which is performed at the same time as extrusion molding, foaming by injection molding,
After extrusion molding, any method such as heating and foaming under pressure or normal pressure may be used. The composite foam according to the present invention is made of resins constituting the sea and islands as described above, and the foaming is determined to some extent by the combination of resins, the quantitative ratio, and the physical properties of the resins (melting point, melt viscosity, etc.). Due to the molding conditions, a kneading improver that improves the compatibility of both resins is added during foam molding to reduce the dispersion unit of the island and improve the peel strength at the sea-island interface. Furthermore, the foaming properties and physical properties of the resulting composite foam can be improved. The kneading property improver used in the present invention has monomer units equivalent to at least one of the resins constituting the sea and the island, and has a structure equivalent to or chemically similar to the other resin. Copolymers composed of monomer units are preferred.
The specific examples vary depending on the combination of resins, etc., but for example, styrene-butadiene copolymer and its hydrogenated product, acrylonitrile-butadiene copolymer, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, methyl Such as methacrylate-styrene copolymer. Furthermore, a resin equivalent to one of the resins constituting the sea and the island is impregnated with a monomer having a structure equivalent to or chemically similar to the monomer unit of the other resin, and then the monomer is polymerized. The modified resin obtained by this process can also be used as a kneading property improver. for example,
Styrene obtained by impregnating polyethylene or polypropylene with styrene monomer under appropriate temperature conditions in an aqueous suspension containing polyethylene or polypropylene, styrene monomer, and a polymerization initiator, and then starting and progressing the polymerization of styrene. Modified polyethylene or polypropylene, etc. Furthermore, the present invention also includes a multilayer sheet having at least one layer of a composite foam made of the above materials and molding method and formed by extrusion molding and/or lamination molding, and a molding method thereof. Although the composite foam according to the present invention can have the same foaming properties as the resin constituting the islands, in order to further improve the foaming properties, and in particular to prevent the generated gas from dissipating from the surface, both outer layers of the foam It is effective to laminate non-foamed resin on the surface of the material by various methods. Furthermore, by laminating, it is possible to improve the appearance, vacuum forming, etc. The method for manufacturing the resin multilayer sheet having at least one layer of foam according to the present invention may be any conventional method, such as wet lamination,
These include dry lamination, hot melt lamination, extrusion lamination, coextrusion lamination, etc. Specifically, a foaming agent is mixed in advance with the resin that will become the islands, and mixed with the resin that will become the sea in an extruder.
After extrusion foaming with a die or circular die, another film or sheet is laminated while the foam is in a molten state, or
After cooling the foam, dry and wet lamination is performed, and the core layer is made of the foam and the skin layer is made of ordinary resin, multilayered in a die, and the core layer is foamed at the same time as extrusion from the die. There are ways to do this. [Example 1] Propylene-ethylene block copolymer (Mitsubishi Yuka Co., Ltd. "Mitsubishi Noblen BC8B" MFR = 1.1) (hereinafter simply referred to as polypropylene) 80wt% polystyrene (Mitsubishi Monsanto Chemical Co., Ltd. "Dialex HT516") Mitsubishi Heavy Industries, Ltd. produced a resin mixture containing 20 wt% of expandable polystyrene, which was previously mixed and granulated in an extruder with 3 wt% of azodicarbonamide and 0.5 wt% of talc as a nucleating agent at below the foam decomposition temperature. Extruded from T die at 200℃ using HM type 50φ extruder manufactured by Co., Ltd. and foamed to a thickness of 1mm.
A sheet-like composite foam was obtained. Table 1 shows the physical properties of this foam. [Comparative Example 1] 99.4wt% of the polypropylene used in Example 1 was blended with 0.6wt% of azodicarbonamide.
Extruded and foamed at 200℃ using a 50φ extruder to a thickness of 1
A sheet-like foam of mm was obtained. Table 1 shows the physical properties of this foam. [Comparative Example 2] Example 1 was used instead of polypropylene in Comparative Example 1.
Using the polystyrene used in , the thickness was 1
A sheet-like foam of mm was obtained. The physical property values are shown in Table 1. [Comparative Example 3] Same as the 79.4 wt% polypropylene used in Example 1, 20 wt% polystyrene and 0.6 wt% azodicarbonamide were extruded and foamed at 200°C using the same extruder to obtain a sheet-like foam with a thickness of 1 mm. Ta. The physical property values are shown in Table 1.

[Example 2]

Low-density polyethylene (Yukalon manufactured by Mitsubishi Yuka Co., Ltd.)
A resin mixture containing 20 wt% of expandable polystyrene beads, which are polystyrene pre-impregnated with 5 wt% of butane, was added to 80 wt% of EH-30'' MFR = 2.0) using a T-die extruder made by Mitsubishi Heavy Industries, Ltd. HM model 50φ.
Extrusion foaming was performed at 160°C to obtain a sheet-like composite foam with a thickness of 0.7 mm. Table 2 shows the physical properties of this foam. [Comparative Example 4] 80wt% low density polyethylene used in Example 2
On the other hand, using the same extruder, a resin mixture containing 20 wt% of beads not impregnated with polystyrene used in Example 2 was used, and butane gas was injected from the middle of the extruder at a ratio of 1 wt% to the mixed resin. Then, it was extruded and foamed at 160°C through a T-die to obtain a sheet-like foam with a thickness of 0.7 mm. Table 2 shows the physical properties of this foam.

[Example 3]

Ethylene-vinyl acetate copolymer (Mitsubishi Yuka Co., Ltd. "Yukalon-Eva EVA41-H" MFR = 2.0, vinyl acetate content 16 wt%) 80 wt% polystyrene (Mitsubishi Monsanto Chemical Co., Ltd. "Dialex")
Mitsubishi Yuka Fine as a blowing agent in advance (HT516)
Using a material containing 20 wt% of expandable polystyrene, which is made by mixing 6 wt% of "Fine Blow S-20N" sold by Co., Ltd. in an extruder at a temperature below the foam decomposition temperature, the material was extruded and foamed at 150°C in the same manner as in Example 1. , 1mm thick
A sheet-like composite foam was obtained. Table 3 shows the physical properties of this foam. [Comparative Example 5] 78.8 wt% of the same ethylene-vinyl acetate copolymer as in Example 3 and the same polystyrene as in Example 3
20wt% and Mitsubishi Yuka Fine Co., Ltd. as a blowing agent.
1.2wt% of the released "Fine Blow S20N" was extruded and foamed at 150℃ through a T-die using an extruder. Table 3 shows the physical properties of this foam.

[Example 4]

80wt% of the polypropylene used in Example 1 and 20wt% of talc were mixed in advance in an extruder, and this material
To the polystyrene used in Example 1, 3 wt% of azodicarbonamide and 0.5 wt% of talc as a nucleating agent were added to 80 wt% of the polystyrene.
A resin mixture containing 20 wt% of expandable polystyrene, which had been mixed in advance in an extruder at a temperature below the foam decomposition temperature, was extruded and foamed at 200°C in the same manner as in Example 1 to obtain a sheet composite foam with a thickness of 1 mm. Ta. Table 4 shows the physical properties of this foam. [Comparative Example 6] Talc-containing polypropylene similar to Example 4
79.4wt% and polystyrene similar to Example 4
20wt% (no foaming agent or nucleating agent added) Furthermore, 0.6wt% of azodicarbonamide as a foaming agent was extruded through a T-die at 200℃ using an extruder and foamed to a thickness of 1mm.
A sheet-like foam was obtained. . Table 4 shows the physical properties of this foam.

【table】

[Example 5]

For 80 wt% of the polypropylene used in Example 1, 3 wt% of azodicarbonamide was mixed and granulated in polystyrene (Mitsubishi Monsanto Chemical Co., Ltd. "Dialex HF77") using an extruder at a temperature below the firing decomposition temperature. A resin mixture containing 20 wt% of expanded polystyrene was molded using a Meiki Seisakusho injection molding machine at an injection pressure of 800 Kg/cm ² and a resin temperature of
Foam molding is performed at 220℃ using the shot shot method, and the length x width x thickness is 36 cm x 10 cm x 0.3 cm.
A plate-shaped composite foam with a size of . Table 5 shows the physical properties of this foam. [Comparative Example 7] A similar plate-shaped foam was obtained using the same injection molding machine and the same conditions as in Example 5 using the same 79.4 wt% polypropylene used in Example 5, 20 wt% polystyrene, and 0.6 wt% azodicarbonamide. Ta. Table 5 shows the physical properties of this foam.

[Example 6]

The same material used in Example 4 was used as a foamed intermediate layer (thickness: 1.0 mm), and the surface layer was made of polypropylene (thickness:
0.1 mm) (Mitsubishi Noblen FY6, manufactured by Mitsubishi Yuka Co., Ltd.), coextrusion foaming was carried out using a combining adapter of two resins and three layers. Table 6 shows the physical properties of the obtained laminated composite foam. [Comparative Example 8] The same material used in Comparative Example 6 was used as a foamed intermediate layer (thickness 1.0 mm), the same polypropylene as in Example 6 (thickness 0.1 mm) was used as the surface layer, and the same method as in Example 6 was carried out. As a result, a sheet-like laminated foam having three layers of two resins was obtained. Table 6 shows the physical properties of this foam.

[Examples 7 to 9]

With the material composition, molding method, and molding temperature shown in Table 7, extrusion molding foaming was performed in Example 1, and injection molding foaming was performed in Example 5.
Various composite foams were obtained in the same manner as above. The foaming agent was mixed in advance at 3wt% with respect to the resin constituting the islands. Table 7 also shows the physical property values of these foams. In any case, compared to a foam using a single resin, the composite foam according to the present invention sufficiently exhibits the characteristics of the resins constituting the sea and the island.

[Example 10]

80wt% of the same polypropylene and 20wt% of talc as in Example 4 were mixed in advance in an extruder, and this material
Azodicarbonamide was added to the same polystyrene as in Example 4 for 70wt%.
20wt% of expandable polystyrene was prepared by mixing 0.5wt% of talc as a nucleating agent with respect to polystyrene in an extruder at a temperature below the foaming decomposition temperature, and polypropylene (MFR=
6.0) was impregnated with styrene monomer, and then a resin mixture containing 10 wt% of styrene-modified polypropylene (polystyrene content: 50 wt%, grafted polystyrene: 30 wt% of the total amount of polystyrene) was prepared in the same manner as in Example 1. in,
The mixture was extruded and foamed at 200°C to obtain a sheet-like composite foam with a thickness of 1 mm. Table 8 shows the physical properties of this foam. [Example 11] All the materials and methods were the same as in Example 10, except that a styrene-butadiene copolymer (Asahi Kasei Kogyo Co., Ltd. "Toughblen A") was used instead of styrene-modified polypropylene as a kneading improver. Thickness 1mm
A sheet-like foam was obtained. Table 8 shows the physical properties of this foam. As can be seen from Table 8, the addition of the kneading improver increases the tensile strength.

【table】

Claims (1)

[Scope of Claims] 1. In a resin-based composite having a sea/island structure, the island portion constitutes a microfoamed part of an amorphous thermoplastic resin, and the sea portion is a crystalline composite that is substantially unfoamed. A composite foam comprising a continuous thin layer of thermoplastic resin. 2. The composite foam according to claim 1, wherein the resin forming the thin layer continuum portion forming the sea is made of a resin that is relatively difficult to dissolve with the resin forming the micro foam portion forming the islands. 3. The composite foam according to claim 1, wherein the continuous thin layer portion forming the sea is made of polyolefin. 4 Claims 1 and 2 in which the thin layer continuum forming the sea contains an inorganic and/or organic filler
Or the composite foam of item 3. 5. The composite foam according to claim 1, 2, 3 or 4, wherein the composite foam is in the form of a sheet. 6 A composition that is composed of an amorphous thermoplastic resin and a crystalline thermoplastic resin that are relatively difficult to dissolve in each other, and has a sea/island structure in which the latter resin constitutes the sea part and the former resin constitutes the island part, mainly consisting of islands. A method for manufacturing a composite foam in which the island portion is formed into a fine foam portion and the sea portion is formed into a thin layer continuous portion that is not substantially foamed by foaming the portion. 7. A chemical foaming agent and/or a physical foaming agent is mixed or impregnated in advance with the resin that is to form the islands, and the resin that is to form the sea is blended with this and then extrusion molding, injection molding, or other methods are used. 7. The method according to claim 6, wherein heating, melting, and foaming are simultaneously carried out by heating, melting, and foaming, or by melting and mixing at a temperature below the foaming temperature to obtain a foamable composition or product, which is then heated and foamed. 8. The method according to claim 6 or 7, wherein the resin to constitute the sea contains an inorganic and/or organic filler. 9 Claims 6, 7 or 8 which include a kneading improver in addition to the resin constituting the sea/island
Section method. 10 A patent claim in which the kneading property improver is a copolymer composed of monomer units equivalent to at least one of the resins constituting the sea or island and monomer units having a structure equivalent to or similar to the other resin. Scope of Item 9 Method. 11 The kneading property improver is a modified resin obtained by impregnating a resin equivalent to one of the resins constituting the sea or island with a monomer having a structure equivalent to or similar to the monomer unit of the other resin, and then polymerizing it. 10. The method of claim 10.