JPH10212368A - Thermoplastic resin foam and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermoplastic resin foam comprising a thermoplastic resin and a reinforcing liquid crystal resin, reinforced at good efficiency by the fibrillated liquid crystal resin, prepared by using a heat-decomposable blowing agent as the blowing agent and having an easily attained high expansion ratio, and to provide a process for producing the same. SOLUTION: This foam comprises 0.1-60wt.% liquid crystal resin and 99.9-40wt.% thermoplastic resin. The liquid crystal resin is in the state of fibrils and substantially oriented in one direction. An example of the process for producing the foam consists of foaming a mixture comprising a liquid crystal resin, a thermoplastic resin and a blowing agent in a one-dimensional direction at a temperature equal to or higher than the transition point of the liquid crystal resin and simultaneously fibrillation and orienting the liquid crystal resin in the direction of foaming during foaming. Another example of the method consists of mixing a mixture comprising a liquid crystal resin and a thermoplastic resin at a temperature equal to or higher than the transition point of the liquid crystal resin, fibrillating first the liquid crystal resin and then foaming the entire in a one-dimensional direction to orient the fabricated liquid crystal resin in the direction of foaming.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin foam, and more particularly, to a thermoplastic resin foam comprising a thermoplastic resin and a liquid crystal resin and having excellent heat deformation resistance and mechanical strength, and a method for producing the same. It is.

[0002]

2. Description of the Related Art Conventionally, thermoplastic resin foams have been widely used for cushioning materials, heat insulators, electric insulators, etc. However, the performance of conventional thermoplastic resin foams is not always sufficient, and It is necessary to improve the heat deformation resistance and mechanical strength, etc., as a method, for example, by dispersing reinforcing fibers such as glass fibers in a thermoplastic resin foam, or by laminating different substrates and the like on the surface. Methods such as joining are known.

For example, Japanese Patent Application Laid-Open No. 4-110129 discloses a method in which a reinforcing material such as glass fiber is dispersed in a thermoplastic resin foam and molded.

Japanese Patent No. 2503109 discloses that a cloth comprising at least a composite fiber and / or a yarn composed of an adhesive component and a reinforcing component is heated and pressed on the surface of a thermoplastic resin foam, and the reinforcing material is used for the reinforcement. A method of reinforcing a thermoplastic resin foam in which a cloth is bonded via an adhesive component is disclosed.

[0005]

However, in the reinforcing method described in the above publication, the thermoplastic resin foam is molded in a state where the reinforcing fibers such as glass fibers are dispersed, so that the fibers cause foam breakage and the expansion ratio is increased. However, there is a problem that it is not possible to obtain a molded product having a high stiffness.

The reinforcing method described in the above publication is effective in improving the rigidity of the plate material and preventing scattering of the thermoplastic resin foam upon impact destruction. However, the weight increases and the strength of the foam layer itself is not improved. Since it does not change, there is a problem that it is not possible to obtain a product sufficiently excellent in heat deformation resistance and mechanical strength.

An object of the present invention is to solve the above-mentioned problems of the prior art, to mix a liquid crystal resin as a reinforcing material of a thermoplastic resin and to efficiently reinforce the liquid crystal resin which has been fibrillated, and to thermally decompose as a foaming agent. It is an object of the present invention to provide a thermoplastic resin foam which can be easily foamed to a high expansion ratio using a mold foaming agent, is lightweight, has high strength, and has excellent heat deformation resistance, and a method for producing the same. .

[0008]

In order to achieve the above-mentioned object, the thermoplastic resin foam according to the present invention has a thickness of 0.1 to 6 mm.
0% by weight of a liquid crystal resin, having a melting point or melting temperature lower than the transition point of the liquid crystal resin, and 99.9 to 40% by weight
Characterized in that the liquid crystal resin is fibril-shaped and substantially oriented in one direction.

Further, the method for producing a thermoplastic resin foam according to the present invention is a method for producing a thermoplastic resin foam, comprising: a liquid crystal resin, a thermoplastic resin having a melting point or melting temperature lower than the transition point of the liquid crystal resin, and a foaming agent. The mixture obtained by mixing at a temperature lower than the transition point is foamed in a one-dimensional direction at a temperature equal to or higher than the transition point of the liquid crystal resin, and at the time of foaming, the liquid crystal resin in a molten state is fibrillated and oriented in the foaming direction. It is characterized by:

[0010] Further, another method for producing a thermoplastic resin foam according to the present invention is a method for converting a liquid crystal resin and a thermoplastic resin having a melting point or melting temperature lower than the transition point of the liquid crystal resin into a liquid crystal resin. A step of dispersing the liquid crystal resin into fibrils by mixing at a temperature not lower than the point and under shear stress, and then adding and mixing a foaming agent to the resulting mixture,
A step of foaming these in a one-dimensional direction at a temperature equal to or lower than the transition point of the liquid crystal resin, and orienting the fibril-shaped liquid crystal resin at the time of foaming.

In the thermoplastic resin foam according to the present invention, the liquid crystal resin dispersed in the thermoplastic resin is dispersed in the form of fibrils and is oriented in one direction, whereby the reinforcing effect of the liquid crystal resin is exhibited. It is excellent in heat deformation resistance, rigidity and strength, and has a high expansion ratio.

In the above, the thermoplastic resin is not particularly limited as long as it is a foamable thermoplastic resin.
For example, ABS resin, ethylene-vinyl acetate copolymer,
Fluororesin, acetal resin, amide resin, imide resin, amide imide resin, acrylic resin, vinyl chloride resin, olefin resin, polyester, polycarbonate, polyacrylate, polyphenylene oxide, polystyrene, thermoplastic polyurethane, etc., and modified or blended materials thereof (Alloy material) and other resins that can be melt-molded. Among these resins, polyolefin, polystyrene, copolymers thereof, and the like are preferable.

[0013] The thermoplastic resin may be crosslinked, if necessary. Use of the crosslinked resin improves the expansion ratio and reduces the weight of the obtained foamed molded article. As well as improving the thermal stability,
It is suitable.

Here, the method of crosslinking is not particularly limited. For example, an electron beam crosslinking method of irradiating ionizing radiation such as an electron beam, a chemical crosslinking method using an organic peroxide,
Alternatively, a silane crosslinking method using a silane-modified resin can be used.

On the other hand, the liquid crystal resin is not particularly limited as long as it has a liquid crystal transition temperature higher than the melting point or melting temperature of the thermoplastic matrix resin. Polyester amides are preferred. Specific examples thereof include wholly aromatic polyester-based liquid crystal polymers marketed under the trade names such as Vectra, Econol, and Zyder, and semi-aromatics marketed under the trade names such as rodrun, novaculate, and LCP. Group polyester-based liquid crystal polymers.

In the present invention, the mixing ratio of the liquid crystal resin to the thermoplastic resin is within a concentration range in which the composition as a whole can be foam-molded, and the ratio is appropriately selected depending on the composition of the thermoplastic resin and the performance required for the product. However, usually 0.1 to
It is composed of 60% by weight of liquid crystal resin and 99.9 to 40% by weight of thermoplastic resin. The content of the liquid crystal resin is preferably 1 to 30 parts by weight, more preferably 3 to 20 parts by weight.

Here, the compounding amount of the liquid crystal resin is 0.1% by weight.
If it is less than the above, the above-mentioned problems cannot be solved, and the effects of the present invention cannot be obtained. If the amount of the liquid crystal resin exceeds 60% by weight, foam breaks are observed everywhere, and a uniform foam having a high expansion ratio cannot be obtained.

The expansion ratio of the thermoplastic resin foam is appropriately selected depending on the composition, the performance required for the product, and the use, but is usually in the range of 2 to 50 times, preferably 2 to 30 times. is there. If the expansion ratio of the thermoplastic resin foam exceeds 50 times, the diameter and distribution of the foam cells become uneven, and a uniform foam molded product cannot be obtained.

In the production of the thermoplastic resin foam of the present invention, the pyrolysis type foaming agent usually used is not particularly limited as long as it has a decomposition temperature higher than the melting temperature of the thermoplastic resin used. Inorganic pyrolytic foaming agents such as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, azide compounds, sodium borohydride; azodicarbonamide, azobisisobutyronitrile, N, N '
-Dinitrosopentamethylenetetramine, P, P'-dinitrosopentamethylenetetramine, P, P'-oxybisbenzenesulfonylhydrazilo, barium azodicarboxylate, trihydrazinotriazine and the like. Azodicarbonamide which is easy to adjust, generates a large amount of gas, and is excellent in hygiene is preferable.

The amount of the pyrolytic foaming agent is 1 to 100 parts by weight of the mixed resin composition of the thermoplastic resin and the liquid crystal resin.
-30 parts by weight are preferred.

If necessary, the mixed resin composition of the liquid crystal resin and the thermoplastic resin may be mixed with each other before or during molding in order to improve the mutual compatibility according to the composition of the liquid crystal resin and the thermoplastic resin. The agent is added. Compatibilizers include:
For example, when the thermoplastic resin is an olefin resin, a copolymer obtained by copolymerizing an olefin component and a styrene component or an aromatic polyester component, an olefin resin copolymer having a maleic acid component or an acrylic acid component, and a glycidyl methacrylate component are used. Olefin resin copolymers.

The number of parts to be added of the compatibilizer is appropriately selected depending on the composition and ratio of the mixed system.

[0023]

Next, an embodiment of the present invention will be described.
This will be described in detail below.

In the foam comprising a liquid crystal resin and a thermoplastic resin according to the present invention, it is necessary that the liquid crystal resin be fibril-like in the thermoplastic resin and be substantially oriented in one direction. By being in the fibril state in this way, it is possible to exhibit high strength and excellent heat deformation resistance.

An external stress such as a shear stress or an elongation stress is applied to a foamable resin composition comprising a thermoplastic resin and a liquid crystal resin at a temperature equal to or higher than the liquid crystal transition point of the liquid crystal resin. The dispersed state can be a fibril state.

The fibril-like liquid crystal resin has an excellent effect of reinforcing the thermoplastic resin foam. The fibril state indicates a state in which the liquid crystal resin dispersed in the thermoplastic resin has at least an aspect ratio (dispersion length / dispersion diameter) of 1.5 or more.

The aspect ratio of the liquid crystal resin fibrils in the present invention is preferably 10 or more. Further, the fibril diameter is preferably 0.1 to 100 μm,
0 μm is more preferred.

The degree of fibrillation of the liquid crystal resin contained in the thermoplastic resin foam of the present invention can be visualized by microscopic observation or soft X-ray observation. In the present invention, it is desirable that at least 10% or more, more preferably 30% or more, of the contained liquid crystal resin is in the form of fibrils.

Further, in the present invention, 60
% Or more is desirably oriented. The degree of orientation at this time is determined by observing a thinly cut thermoplastic resin foam with an optical microscope and analyzing the image. To elaborate,
First, the reference orientation direction is determined, and the angle is defined as the ratio of the fibrils having an angle of 45 ° or more and 90 ° or less with the plane perpendicular to the orientation direction and the fibrils.

Next, a second aspect of the present invention will be described.

According to the second aspect of the present invention, the thermoplastic resin, the liquid crystal resin and the foaming agent are first melted at a temperature lower than the transition point of the liquid crystal resin and lower than the decomposition temperature of the foaming agent. Kneading to obtain a primary mixed resin molded product.

Here, in order to obtain a primary mixed resin molded article,
A resin composition containing a thermoplastic resin, a liquid crystal resin, and a pyrolytic foaming agent may be melt-kneaded by a general method, and the specific method is not particularly limited.

Usually, a liquid crystal resin and a thermoplastic resin having a melting point or melting temperature lower than the transition point temperature of the liquid crystal resin are used.

Next, when the thermoplastic resin used is a crosslinkable resin, the primary mixed resin molded product is subjected to a crosslinking treatment.

Next, the primary mixed resin molded product is foamed in one direction.

In this method, for example, the primary mixed resin molded body is placed in a box-shaped mold opened in only one direction, and foamed at a temperature equal to or higher than the transition point of the liquid crystal resin.

Thereafter, the foam is cooled to a temperature lower than the softening temperature of the thermoplastic resin and solidified, whereby a liquid crystal resin fibrillated and a one-dimensionally oriented thermoplastic resin foam can be obtained. . In this case, the method of heating and cooling is not particularly limited.

[0038] Alternatively, the primary mixed resin molded article may be formed into a sheet, a sheet-like material for suppressing foaming in the surface direction may be laminated on the sheet-shaped primary mixed resin molded article, and then foamed. Similarly, a thermoplastic resin foam in which the liquid crystal resin is fibrillated and oriented in the thickness direction can be obtained.

The fibril-like liquid crystal resin has an excellent effect of reinforcing the thermoplastic resin foam.

Next, a third aspect of the present invention will be described.

In the method for producing a thermoplastic resin foam according to the present invention, the thermoplastic resin and the liquid crystal resin are first heated at a temperature higher than the transition point of the liquid crystal resin, for example, in an extruder or a mold. The liquid crystal resin can be easily made into a fibril shape by melt-kneading while applying shear.

At this time, the form of the obtained mixture is desirably in the form of pellets or particles in consideration of mixing with the following pyrolytic foaming agent.

Next, a mixture of a thermoplastic resin and a liquid crystal resin and a pyrolytic foaming agent are melt-kneaded at a temperature lower than the transition point of the liquid crystal resin and lower than the decomposition temperature of the foaming agent to obtain a primary mixed resin molded article.

Next, when the thermoplastic resin used is a crosslinkable resin, the primary mixed resin molded article is subjected to a crosslinking treatment.

Next, the primary mixed resin molded article is foamed in one direction by the same method as the foaming method described in claim 2, so that the fibrillated liquid crystal resin is oriented in one-dimensional direction. Obtain a foam.

In any case, additives such as a flame retardant, a filler, an antioxidant, a nucleating agent, and a pigment may be added to the resin composition as long as the effects of the present invention are not impaired. May be blended. Such additives are widely known,
For example, as a flame retardant, hexabromobiphenol ether, and brominated flame retardants such as decabromodiphenyl ether, ammonium polyphosphate, phosphorus-containing flame retardants such as trimethyl phosphate and triethyl phosphate,
Melamine derivative flame retardants, inorganic flame retardants, and the like.

(Function) According to the present invention, the liquid crystal resin is dispersed in the form of fibrils by foaming the mixed resin composition comprising the thermoplastic resin, the liquid crystal resin, and the pyrolytic foaming agent in one dimension. A thermoplastic resin foam having high strength oriented in one direction and having excellent heat deformation resistance can be obtained.

[0048]

EXAMPLES Next, examples of the present invention will be described together with comparative examples, but the present invention is not limited to only these examples.

Example 1 A liquid crystal resin (trade name: Rodrun LC-5000, transition point 2)
85 ° C, manufactured by Unitika Ltd.) 10% by weight, as a thermoplastic resin, a non-crosslinked polypropylene resin (melting point 165 ° C,
MI = 10) 90 parts by weight of an olefin resin composed of 70 parts by weight and 30 parts by weight of a silane crosslinkable homopolypropylene (trade name: XPM800H, manufactured by Mitsubishi Chemical Corporation), and 100 parts by weight of these resins, azodicarbonate as a foaming agent A compound consisting of 11 parts by weight of amide (decomposition starting temperature: 200 ° C.) was melt-kneaded by a twin-screw extruder set at a cylinder temperature of 185 ° C., and a die having a sheet-shaped product extrusion port (exit width: 100 mm, same thickness) (1 mm) to obtain a molded product.

The molded body was immersed in hot water at 100 ° C. to perform a crosslinking treatment.

The molded body is 100 mm long × 100 mm wide.
, And the sheet is laid on the bottom of a box-shaped mold having a size of 100 mm x 100 mm, which is opened only at the top and having a bottom size of 100 mm x 100 mm.
A thermoplastic resin foam having a thickness of 00 mm and a thickness of 20 mm was obtained. The expansion ratio at this time was 18 times.

When the thermoplastic resin foam was fractured under liquid nitrogen and the fractured surface was observed with an electron microscope, it was found that most of the liquid crystal resin was present in the form of fibrils in the polypropylene forming the cell membrane and was substantially in the form of fibrils. In particular, 80% of the fibrils were oriented in one direction.

Example 2 A liquid crystal resin (trade name: Rodrun LC-5000, transition point 2)
85 ° C, manufactured by Unitika Ltd.) 10% by weight, as a thermoplastic resin, a non-crosslinked polypropylene resin (melting point 165 ° C,
MI = 10) A compound comprising 90 parts by weight of an olefin resin consisting of 70 parts by weight and 30 parts by weight of a silane crosslinkable homopolypropylene (trade name: XPM800H, manufactured by Mitsubishi Chemical Corporation) is biaxially extruded at a cylinder temperature of 290 ° C. The mixture was melt-kneaded by a machine, extruded into strands, and then cut to obtain mixed pellets. At this time, when the form of the liquid crystal resin was observed with an electron microscope (500 times magnification), most of the liquid crystal resin was fibrillated.

With respect to 100 parts by weight of the obtained pellets,
11 parts by weight of azodicarbonamide (decomposition onset temperature 20
0 ° C.) is melt-kneaded in a twin-screw extruder set at a cylinder temperature of 185 ° C., and extruded with a die having a sheet-shaped product extrusion port (exit width 100 mm, same thickness 1 mm); A molded article was obtained.

The molded body was immersed in hot water at 100 ° C. to perform a crosslinking treatment.

This molded product is 100 mm long × 100 mm wide.
, And the sheet is laid on the bottom of a box-shaped mold having a size of 100 mm x 100 mm, which is opened only at the top and having a bottom size of 100 mm x 100 mm.
A thermoplastic resin foam having a thickness of 00 mm and a thickness of 20 mm was obtained. The expansion ratio at this time was 18 times.

When the thermoplastic resin foam was broken under liquid nitrogen and the cut surface was observed with an electron microscope, most of the liquid crystal resin remained in the form of fibrils in the polypropylene forming the cell membrane. And substantially 80% of the fibrils were oriented in one direction.

COMPARATIVE EXAMPLE 1 For comparison, the molded article obtained in the same procedure as in Example 2 was heated in an oven at 220 ° C. without restriction until the cross-linking treatment, and foamed. A resin foam was obtained. The expansion ratio at this time was 18 times.

As a result, most of the liquid crystal resin was present in the form of fibrils in the polypropylene forming the cell membrane of the thermoplastic resin foam, but the orientation was random.

Comparative Example 2 A thermoplastic resin foam was obtained in the same manner as in Comparative Example 1 except that no liquid crystal resin was contained. The expansion ratio at this time is 1
It was 9 times.

[Evaluation of Expanded Molded Article] The thermoplastic resin foams obtained in the above Examples and Comparative Examples were placed in a thermostat, and the temperature of the atmosphere was raised from 30 ° C. (T1) to 60 ° C. (T2). The length of the foam at a temperature of 30 ° C .: L1, and the length of the foam at a temperature of 60 ° C .: L2 The dimensional change in the length direction was measured, and the rate of change of the length was divided by the temperature difference.
The coefficient of thermal expansion was determined.

Thermal expansion coefficient (α) = ((L2−L1) / L
1) / (T2-T1) Further, the 25% compressive strength was measured according to JIS K6767, and the obtained results are shown in Table 1.

[0063]

[Table 1] As is clear from the results in Table 1, the thermoplastic resin foam of the example of the present invention had a very high compressive strength and had sufficient mechanical strength and rigidity. Further, the thermal expansion coefficient of the thermoplastic resin foam of the example of the present invention was very small, and therefore, it was excellent in heat deformation resistance and dimensional stability.

On the other hand, the thermoplastic resin foam of the comparative example has low compressive strength, does not have sufficient mechanical strength and rigidity, and has a large coefficient of thermal expansion. And the dimensional change was large.

[0065]

As described above, the thermoplastic resin foam of the present invention has 0.1 to 60% by weight of a liquid crystal resin, a melting point or a melting temperature lower than the transition point of the liquid crystal resin, and 9% by weight.
A foam comprising 9.9 to 40% by weight of a thermoplastic resin, wherein the liquid crystal resin is fibril-like and substantially oriented in one direction. According to the thermoplastic resin foam, the liquid crystal resin is dispersed in a fibril form in the thermoplastic resin, and the reinforcing effect of the liquid crystal resin is exhibited. Therefore, the thermoplastic resin foam has excellent rigidity and mechanical strength. It is excellent in heat deformation resistance and dimensional stability. It can be easily foamed to a high expansion ratio, and it is lightweight. In addition, liquid crystal resin can be re-melted, so thermoplastic foam The body is reusable.

One of the methods for producing a thermoplastic resin foam of the present invention comprises, as described above, a liquid crystal resin, a thermoplastic resin having a melting point or melting temperature lower than the transition point of the liquid crystal resin, and a foaming agent. And the mixture obtained by mixing at a temperature lower than the transition point of the liquid crystal resin is foamed in a one-dimensional direction at a temperature equal to or higher than the transition point of the liquid crystal resin. Another method for producing a thermoplastic resin foam according to the present invention comprises, as described above, a liquid crystal resin and a melting point or melting temperature lower than the transition point of the liquid crystal resin. A thermoplastic resin having a temperature of not less than the transition point of the liquid crystal resin and under a shear stress to disperse the liquid crystal resin in a fibril state, and then add a foaming agent to the resulting mixture and mix. ,these Foaming in a one-dimensional direction at a temperature lower than the transition point of the liquid crystal resin, and orienting the fibril-shaped liquid crystal resin at the time of foaming. By foaming a mixture of resin and a foaming agent in one direction,
In the thermoplastic matrix resin, since the liquid crystal resin is present in the form of fibrils dispersed therein, the reinforcing effect of the liquid crystal resin is sufficiently exhibited, and the obtained thermoplastic resin foam has excellent rigidity, and excellent mechanical strength. And heat-resistant deformation,
It has excellent dimensional stability.

Since the foam can be easily foamed to a high expansion ratio, the obtained foam is lightweight and
Since the liquid crystal resin can be re-melted, there is an effect that the thermoplastic resin foam can be reused.

Claims (3)

[Claims] 1. A foam comprising 0.1 to 60% by weight of a liquid crystal resin and 99.9 to 40% by weight of a thermoplastic resin having a melting point or melting temperature lower than the transition point of the liquid crystal resin. Wherein the liquid crystal resin is fibril-shaped and substantially oriented in one direction. 2. A mixture obtained by mixing a liquid crystal resin, a thermoplastic resin having a melting point or melting temperature lower than the transition point of the liquid crystal resin, and a foaming agent at a temperature lower than the transition point of the liquid crystal resin. Is foamed in a one-dimensional direction at a temperature equal to or higher than the transition point of the liquid crystal resin, and the liquid crystal resin is fibrillated at the time of foaming and is oriented in the foaming direction. 3. A liquid crystal resin and a thermoplastic resin having a melting point or melting temperature lower than a transition point of the liquid crystal resin,
A step of mixing the liquid crystal resin in a fibril state by mixing at a temperature equal to or higher than the transition point of the liquid crystal resin and under shear stress, and then adding and mixing a foaming agent to the obtained mixture and mixing these with the transition point of the liquid crystal resin. Foaming in a one-dimensional direction at the following temperature to orient the fibril-shaped liquid crystal resin at the time of foaming.