JP2006289679A - Thermoplastic resin foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic resin foam, which has an open-cell structure, capable of being produced at a low cost by a method substantially comprising a single process. <P>SOLUTION: The thermoplastic resin foam with an open cell ratio of 20% or above comprises a thermoplastic resin with a gel ratio of 1-35 wt.%. A fibrous material with an aspect ratio of 5-500 of 5-100 pts.wt. is added to 100 pts.wt. of the thermoplastic resin and a chemical foaming agent is added to the thermoplastic resin. The obtained composition is heated to the decomposition temperature of the chemical foaming agent or above to obtain the thermoplastic resin foam. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermoplastic resin foam, and more particularly to a thermoplastic resin foam having an open-cell structure obtained by heating and foaming a thermoplastic resin containing a fibrous material.

Thermoplastic resin foams are widely used for cushioning materials and heat insulating materials because they are superior in terms of secondary processability and recycling compared to thermosetting resin foams. It is also possible to obtain a soundproofing material having sound absorbing properties by forming continuous bubbles.
However, when a thermoplastic resin is heated and foamed using a chemical foaming agent or the like, there is a problem that it is difficult to obtain an open-cell structure due to the thermoplasticity. In the past, in order to make a thermoplastic resin foam into an open cell, for example, a method of destroying a bubble cell by mechanical deformation after foam molding (see, for example, Patent Document 1), a bubble cell by microwave irradiation. As described in the method of destroying the material (for example, see Patent Document 2), the method of foaming in two stages (for example, see Patent Document 3), etc. The increase in cost was a problem.
Japanese Patent Laid-Open No. 11-315161 JP-A-10-235670 Japanese Patent No. 2872505

  In view of the above problems, an object of the present invention is to provide a thermoplastic resin foam having an open-cell structure that can be produced at low cost by a method substantially consisting of a single step by chemical foaming.

  As a result of intensive studies to solve the above-mentioned problems, the inventors have added a specific amount of a specific fibrous material to a thermoplastic resin and chemically foamed it so as to have a specific gel fraction. The present inventors have found that a thermoplastic resin foam having a specific open-cell structure can be produced at low cost by heating and foaming comprising the steps.

  That is, according to 1st invention of this invention, it is a thermoplastic resin foam of the open cell ratio 20% or more which consists of a thermoplastic resin with a gel fraction of 1-35 wt%, Comprising: With respect to 100 weight part of thermoplastic resins Thus, a thermoplastic resin foam obtained by adding 5 to 100 parts by weight of a fibrous material having an aspect ratio of 5 to 500 is foamed.

  Further, according to the second invention of the present invention, in the first invention, the thermoplastic resin foam is obtained by adding a chemical foaming agent to the thermoplastic resin and heating it to a temperature equal to or higher than a decomposition temperature of the chemical foaming agent. A thermoplastic resin foam characterized by being a shaped foam is provided.

  According to the third invention of the present invention, there is provided a thermoplastic resin foam characterized in that, in the first or second invention, the fibrous material is an inorganic compound.

  According to the fourth aspect of the present invention, in any one of the first to third aspects, the thermoplastic resin is crystalline such as polypropylene, polyethylene, ethylene propylene copolymer, or ethylene vinyl acetate copolymer. There is provided a thermoplastic resin foam characterized by being a thermoplastic resin.

  Moreover, according to the fifth invention of the present invention, in any one of the first to fourth inventions, the foamed thermoplastic resin has an open cell rate of 20% or more upon completion of the foaming process consisting essentially of a single process. A thermoplastic resin foam is provided.

  Since the thermoplastic resin foam of the present invention is a cross-linked thermoplastic resin foam obtained by blending a fibrous material having an aspect ratio of 5 to 500 with a thermoplastic resin and heating and foaming at a temperature equal to or higher than the decomposition temperature of the chemical foaming agent. After foaming, the cell of the cell is ruptured and opened at the time of foaming, and the foam is obtained by foaming so as to hold the cell hole by the fiber thickening / reinforcing effect and form an open cell structure. It is a thermoplastic resin foam by a method.

  The present invention is a foam having an open cell structure obtained by blending a fibrous material with a thermoplastic resin, foaming and crosslinking. Below, the manufacturing method of a thermoplastic resin, a fibrous material, a foam, etc. are demonstrated in detail.

1. Thermoplastic Resin The thermoplastic resin used in the present invention is not particularly limited as long as it is a commonly used thermoplastic resin. For example, polypropylene, polyethylene, ethylene / propylene copolymer, ethylene / propylene / diene ternary copolymer. Polymers, polyolefins such as ethylene / vinyl acetate copolymer, vinyl copolymers such as polyvinyl chloride and polyvinyl acetate, resins such as polyamide, polycarbonate, polystyrene, polyester, polyhydroxy ether, and the like A random copolymer, a block copolymer, etc. are mentioned. In the present invention, these thermoplastic resins may be used alone or in combination, but after forming an open-cell structure by heating foaming, a crystallization rate is required to maintain the structure by cooling and solidification. It is preferable to contain a crystalline resin having a high speed.
Among these, crystalline resins such as polypropylene, polyethylene, ethylene / propylene copolymer, and ethylene / vinyl acetate copolymer are particularly preferable.

  Moreover, you may add thermosetting resins, such as a urea type, a melamine type, a resorcinol type, a phenol type, an epoxy type, a polyurethane type, a polyester type, an alkyd type, to the said thermoplastic resin as needed.

  In order to impart foamability, the thermoplastic resin needs to have a gel fraction of 1 to 35 wt% by introduction of a crosslinked structure or the like, preferably 1 to 30 wt%, more preferably 1 to 25 wt%. It is. If the gel fraction exceeds 35 wt%, the viscosity will be too high and it will not be suitable for foaming. On the other hand, when the gel fraction is less than 1 wt%, the viscosity necessary for foaming cannot be obtained.

  The method for introducing a crosslinked structure into the thermoplastic resin is not particularly limited as long as it is generally used. Crosslinking with radicals such as organic peroxides, crosslinking with ionizing radiation or UV, and ethylene in the presence of divinyl monomer. Examples thereof include chemical crosslinking such as thermal polymerization using glycol or methylenebisacrylamide, and photopolymerization using a peroxide or an azobis compound as a photosensitizer. In the present invention, the chemical crosslinking method using a peroxide or a crosslinking monomer is preferable because it can be performed simultaneously with foaming.

A chemical crosslinking method using a peroxide or a crosslinking monomer is a method in which a peroxide or a crosslinking monomer is added to a thermoplastic resin, melt-kneaded at a temperature lower than the decomposition temperature of the peroxide, and then heated and crosslinked. Is mentioned. The peroxide used in this method is not particularly limited, and examples thereof include dibutyl peroxide, dicumyl peroxide, tertiary butyl cumyl peroxide, diisopropyl peroxide, and the like, since the decomposition temperature is in an appropriate temperature range. Dicumyl peroxide and tertiary butyl cumyl peroxide are preferable, and dicumyl peroxide is particularly preferable. Examples of the crosslinking monomer include dioxime compounds, acrylic polyfunctional monomers, (meth) acrylic polyfunctional monomers, and quinone compounds.
The blending amount of the peroxide and the crosslinking monomer is preferably 0.1 to 10 parts by weight, particularly preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin. If the amount of peroxide or crosslinking monomer added is too large, the resin decomposition reaction or crosslinking reaction proceeds violently, making it difficult to obtain a foam, and the resulting foam is colored. Further, it is not preferable because crosslinking of the thermoplastic resin may be insufficient.

Here, the gel fraction of the thermoplastic resin foam is determined as follows.
First, a thermoplastic resin foam Ag is weighed, and a residue weight Bg burned in a crucible at 540 ° C. for 6 hours is measured. Also, the thermoplastic resin foam Cg is crushed with a press or the like so that the solvent can easily penetrate into a sheet, and this is immersed in a solvent in which the thermoplastic resin can be dissolved (eg, 120 ° C. xylene in the case of an olefin resin) for 24 hours. The insoluble matter is filtered through a 200-mesh wire mesh, the residue on the wire mesh is vacuum-dried, and the dry residue Dg is measured.
Gel fraction (% by weight) = (1−B / A) × (D / C) × 100

2. Fibrous material Although the fibrous material used by this invention will not be restrict | limited especially if it can mix | blend with a thermoplastic resin, the aspect-ratio needs to be 5-500, Preferably it is 10-400. If the aspect ratio is too low, it is difficult to obtain a thickening / reinforcing effect by the fiber, and if it is too high, the foamability is impaired.
Here, the aspect ratio represents the ratio of the length to the diameter of the fibrous material.

  Examples of fibrous materials that can be used in the present invention include inorganic compound fibers and organic compound fibers. Examples of inorganic compound fibers include glass fibers, amorphous fibers such as rock wool, wollastonite, and titanic acid. Examples thereof include single crystal fibers such as potassium fibers, and polycrystalline fibers such as carbon fibers and alumina fibers. Examples of the organic compound fibers include aramid fibers, polyester fibers, olefin fibers such as (ultra high molecular weight) polyethylene fibers, natural fibers such as cellulose fibers, polyvinyl alcohol fibers, rubber organic fibers, and the like. Furthermore, you may modify | reform such as surface treatment to these fibrous materials as needed.

  The amount of the fibrous material used in the present invention is 5 to 100 parts by weight, preferably 10 to 80 parts by weight, more preferably 15 to 70 parts by weight with respect to 100 parts by weight of the thermoplastic resin. . If the blending amount of the fibrous material is too small, it is difficult to obtain a thickening / reinforcing effect by the fiber, and if it is too large, the foaming property is impaired.

3. Production method of foam The thermoplastic resin foam of the present invention is obtained by foaming a thermoplastic resin composition in which a fibrous material is blended with the thermoplastic resin, and the foaming method of the thermoplastic resin is generally used. Although it will not specifically limit if it is, The method using a thermal decomposition type chemical foaming agent is preferable on production.
Representative examples of the thermal decomposition type chemical blowing agent include azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide) and the like. These may be used alone or in combination of two or more.
The amount of the chemical foaming agent is preferably 1 to 25 parts by weight with respect to 100 parts by weight of the thermoplastic resin. If the amount of the chemical foaming agent is too large, it is easy to break the bubbles, and conversely, if the amount is too much, it will not foam.

  In addition, the thermoplastic resin foam of the present invention includes a bubble forming agent such as calcium carbonate, talc, clay, magnesium oxide; 2,6-di-t-butyl as long as the physical properties of the thermoplastic resin foam are not impaired. -Phenols such as p-cresol, phosphorus-based, amine-based, sulfur-based antioxidants such as dilauryl thiopropionate; methylbenzotriazole metal-damaging agents; halogens such as hexabromobiphenyl ether and decabromodiphenyl ether Non-halogenated flame retardants such as aluminum hydroxide and magnesium hydroxide; in addition to phosphorus flame retardants such as ammonium polyphosphate and trimethyl phosphate, fillers, antistatic agents, stabilizers, pigments, etc. are added May be.

  The thermoplastic resin composition is lower than the decomposition temperature of the pyrolytic foaming agent in an extruder or the like by blending the thermoplastic resin with a fibrous material, a chemical foaming agent, and if necessary, a peroxide. It is melt-kneaded at a temperature to form a thermoplastic resin foam raw material. The obtained foam raw material is shaped according to the final product. As the shaping method, in addition to extrusion molding, methods generally used in plastic molding, such as press molding, blow molding, calendering molding, and injection molding, can be applied. Among these, the method of directly shaping the foamable resin composition discharged from the screw extruder is preferable from the viewpoint of productivity. In this case, it is possible to obtain a continuous foam raw material having a constant width.

  Foaming of the original foam is usually performed at a temperature not lower than the decomposition temperature of the pyrolytic organic foaming agent and not higher than the decomposition temperature of the thermoplastic resin. In particular, as a continuous foaming apparatus, in addition to a take-up type foaming machine that foams while taking up a foam on the outlet side of a heating furnace, a continuous belt type foaming machine, a vertical or horizontal foaming furnace, a hot air thermostatic bath, or a hot bath Oil baths, metal baths, salt baths, etc. that foam are used.

Although the magnification of the thermoplastic resin foam obtained by the present invention is not particularly limited, it is 2 to 40 times, more preferably 5 to 30 times. If the expansion ratio is too small, the lightness is impaired, and if it is too large, the rigidity and the like are impaired.
Here, the expansion ratio of the foam is a value expressed as the reciprocal of the apparent density measured in accordance with JIS K722.

Foaming in the present invention is substantially a single process, and is a continuous process until the foam is obtained by heating and cooling / solidifying the foam material in the foaming process. After the solidification, the thermoplastic resin foam is characterized by being open-celled.
The thermoplastic resin foam of the present invention is open-celled, and the open cell ratio is 20% or more, preferably 20 to 100%.
When the open cell ratio is 20% or more, the foam has effects of sound absorption, air permeability, and flexibility, and can be effectively used for applications such as soundproofing materials, filters, and cushioning materials.
Here, the open cell ratio of the foam is a value measured according to ASTM D2856.

  The present invention will be specifically described by the following examples, but the present invention is not limited thereto. In addition, the analysis and the measuring method of the thermoplastic resin foam in this invention are shown below.

(1) Gel fraction: Thermoplastic resin foam Ag is weighed, and the residual weight Bg burned in a crucible at 540 ° C. for 6 hours is measured. Also, the thermoplastic resin foam Cg is crushed with a press or the like so that the solvent can easily penetrate into a sheet, which is immersed in xylene for 24 hours, insoluble matter is filtered through a 200 mesh wire mesh, and the residue on the wire mesh is vacuumed. It dried and measured the dry residue Dg, and computed by the following formula.
Gel fraction (% by weight) = (1−B / A) × (D / C) × 100
(2) Open cell ratio: Measured according to ASTM D2856 (air pycnometer method).
(3) Foaming ratio: It was determined from the reciprocal of the apparent density measured according to JIS K7222.

Example 1
(1) Molding of foam raw material As a thermoplastic resin, a polypropylene resin (PP) “Novatech PP EG8” (MFR = 0.8 g / 10 min, density = 0.9 g / cm ³ ) manufactured by Nippon Polypro Co., Ltd. is used. Using a dioxime compound (“Barnock GM-P” manufactured by Ouchi Shinsei Kagaku Co., Ltd.) as a monomer for crosslinking, 50 parts by weight and 0.45 parts by weight of the same direction rotating twin screw extruder manufactured by Plastic Engineering Laboratory Co., Ltd. The mixture was put into BT40 and melted and mixed at a set temperature of 240 ° C. This thermoplastic resin mixture is fed in a tandem connection from the tip of the BT40 to a Nippon Steel Corporation co-rotating twin screw extruder TEX44, and further, a thermoplastic block polypropylene / polypropylene resin (BPP) (Nippon Polypropylene). “NOVATEC PP BC3B”, MFR = 9 g / 10 min, density = 0.9 g / cm ³ ), 30 parts by weight, linear low density polyethylene (LLDPE) (Novatech LL UJ370, manufactured by Nippon Polypro, MFR = 16 g) / 10 min, density = 0.92 g / cm ³ ), 20 parts by weight, glass fiber as a fibrous material (“Mildo Fiber MF20JH1-20” manufactured by Asahi Fiber Glass Co., Ltd., fiber diameter = 10 μm, average fiber length = 200 μm, aspect ratio 20 ) 20 parts by weight, azodicarbonamide (ADC) manufactured by Eiwa Chemical Co., Ltd. as a foaming agent ) To "VINYFOR AC # K3" 7.5 parts by weight was charged from the feeder to obtain a thermoplastic resin foam raw sheet having a thickness of about 0.4mm by extruding at a set temperature 180 ° C..

(2) Foaming operation Using a horizontal foaming machine (manufactured by Kyowa Engineering Co., Ltd.) with a total length of 6 m consisting of three zones: preheating zone, foaming zone, and cooling zone, the preheating zone is 190 ° C, the foaming zone is 230 ° C, and the surface temperature of the cooling roll Was set to 90 ° C., respectively. When foaming the raw sheet, a PET film (Teijin DuPont Films, “Tetron” SG 25 μm) is fused on both sides of the front and back surfaces of the foamable resin composition sheet in the preheating zone. While being supplied to the foaming zone, a foam sheet having a good appearance was obtained from the outlet of the foaming machine by foaming and cooling. The results of the obtained foam are shown in Table 1. Moreover, the microscope picture of the bubble cell of a foam is shown in FIG.

(Example 2)
(1) Shaping of foamed raw material As a thermoplastic resin foam, an ethylene / vinyl acetate copolymer “Evertate H-1011” (MFR = 0.6 g / 10 min, density = 0.94 g / cm ³ ) manufactured by Sumitomo Chemical Co., Ltd. 100 parts by weight, organic peroxide as a resin cross-linking agent (Nippon Yushi Co., Ltd. “Park Mill D-40” 1.5 parts by weight, and fibrous material Wollastonite “long fiber wollastonite SH-800 "(Aspect ratio 10) 25 parts by weight, Ewaso Chemical Co., Ltd. azodicarbonamide (ADCA)" Vinole AC # K3 "as a foaming agent, 8 parts by weight, counter-rotating twin screw extruder (Ikegai Iron Works, PCM -30], melt-kneaded at a temperature of 180 ° C., and extruded to obtain a thermoplastic resin foam raw sheet having a thickness of about 0.7 mm.
(2) Foaming operation The foaming operation similar to Example 1 was performed, and the foam sheet with a favorable external appearance was obtained. The results of the obtained foam are shown in Table 1.

(Comparative Example 1)
In Example 1, (1) Foaming material having a good appearance was obtained by shaping and foaming the raw sheet in the same manner except that the predetermined fibrous material was not added. . The results of the obtained foam are shown in Table 1. Moreover, the microscope picture of the bubble cell of a foam is shown in FIG.

(Comparative Example 2)
In Example 1, (1) About the forming of the original foam sheet, the original sheet was shaped and foamed in the same manner except that the addition amount of the oxime compound was 1.0 part by weight and the set temperature was 220 ° C. The foam was not obtained. The obtained results are shown in Table 1.

(Comparative Example 3)
In Example 1, (1) About the forming of the raw foam, the raw material was exactly the same except that the glass fiber “chopped strand CS 13 JA FT689” (aspect ratio 1300) manufactured by Asahi Fiber Glass Co., Ltd. was used as the fibrous material. Although the anti-sheet was shaped and foamed, no foam was obtained. The obtained results are shown in Table 1.

  As is apparent from Table 1, when a fibrous material having an aspect ratio in the range of 5 to 500 is blended with a thermoplastic resin and crosslinked and foamed so that the gel fraction is in the range of 1 to 35% by weight, A foam having an open cell ratio is obtained (Examples 1 and 2). On the other hand, if a fibrous material is not used, a foam having an open cell structure cannot be obtained (Comparative Example 1), and a thermoplastic resin having a crosslinked structure having a gel fraction that is too high does not foam (Comparative Example 2). When a fibrous material having an excessively high aspect ratio is used, foaming does not occur (Comparative Example 3). Moreover, it can be seen from the micrograph that the foam of Example 1 has an open cell structure and the foam of Comparative Example 1 does not have an open cell structure.

  Since the thermoplastic foam of the present invention is an open-celled foam obtained by a process consisting essentially of a single process, it can be produced at a low cost, and the open cell rate is 20% or more. It has excellent properties and flexibility, and can be used effectively for applications such as soundproofing materials, filters, and cushioning materials.

2 is a micrograph of a foam cell of the foam of Example 1. FIG. 2 is a micrograph of a foam cell of a foam of Comparative Example 1.

Claims (5)

  A thermoplastic resin foam made of a thermoplastic resin having a gel fraction of 1 to 35 wt% and having an open cell ratio of 20% or more, and 5% of a fibrous material having an aspect ratio of 5 to 500 with respect to 100 parts by weight of the thermoplastic resin. A thermoplastic resin foam obtained by adding ~ 100 parts by weight and foaming.   2. The heat according to claim 1, wherein the thermoplastic resin foam is a foam shaped by adding a chemical foaming agent to the thermoplastic resin and heating to a temperature equal to or higher than a decomposition temperature of the chemical foaming agent. Plastic resin foam.   The thermoplastic resin foam according to claim 1 or 2, wherein the fibrous material is an inorganic compound.   The thermoplastic resin according to any one of claims 1 to 3, wherein the thermoplastic resin is a crystalline thermoplastic resin such as polypropylene, polyethylene, ethylene propylene copolymer, or ethylene vinyl acetate copolymer. Plastic resin foam.   The thermoplastic resin foam according to any one of claims 1 to 4, wherein the thermoplastic resin foam has an open cell ratio of 20% or more upon completion of a foaming step consisting essentially of a single step. .

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