JPH11179829A - Thermoplastic resin foam and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin foam which is almost free from irregularities in thickness precision and weight precision and has high shock- absorbing properties and compression strength and further, a low level of scattering of strength as well as a method for manufacturing the thermoplastic resin foam at a high productivity. SOLUTION: This thermoplastic resin foam 1 of a plate-like body comprises a continuous cell layer 2 formed of a thermoplastic sin, high-level foamed parts 3 formed of thermoplastic resin arranged on at least, one of the faces of the continuous cell layer 2 and low-level foamed thin coats 4 formed of the thermoplastic resin coating the outer faces of the high-level foamed parts 3 together with the continuous cell layer 2. In this case, when the foam 1 is projected onto a plane of projection which is orthogonal with the thickness direction, the projection is composed of a continuous area onto which only the continuous cell layer 2 is projected and a discontinuous area onto which the continuous cell layer 2, the low-level foamed thin coats 4 and the high-level foamed parts 3 are projected. Further, the region of the foam 1 corresponding to the discontinuous area is formed into a projecting shape with respect to the region of the foam 1 corresponding to the continuous area at least on one surface.

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 a method for producing the same, and more particularly, to an uneven thermoplastic resin foam which enables pseudo one-dimensional foaming in a thickness direction and a method for producing the same. About the method.

[0002] Throughout the present specification, a plate-like body and a sheet-like body are defined based on a relative thickness before and after production of a foam, and are strictly defined based on an absolute thickness. It does not mean a thing but a relatively thin thing usually called a sheet or a film, respectively.

[0003]

2. Description of the Related Art Thermoplastic foams are lightweight and have excellent cushioning properties. Therefore, various types of heat insulating materials such as roof heat insulating materials, ceiling materials for vehicles or heat insulating materials for floors, cushioning materials, flotation materials, or irregularly shaped materials are used. Widely used in products.

As a method for producing a thermoplastic resin foam as described above, conventionally, a foamable thermoplastic resin composition containing a pyrolytic foaming agent is foamed by heating it to a temperature not lower than the decomposition temperature of the foaming agent. Thus, a method for obtaining a thermoplastic resin foam is widely used. When foaming the foamable thermoplastic resin composition, foaming is performed by the pressure of gas generated by the decomposition of the foaming agent contained therein. Therefore, since the expandable thermoplastic resin usually foams and expands almost three-dimensionally and evenly, when manufacturing the thermoplastic resin foam, particularly, continuously manufacture the long thermoplastic resin foam. In this case, it is necessary to cope with the occurrence of wrinkles due to expansion in the width direction and the longitudinal direction.

For example, according to the method described in Japanese Patent Publication No. 48-9955, a continuous foamable thermoplastic resin sheet containing a foaming agent is fed, heated and foamed to obtain a thermoplastic resin foam. When winding the thermoplastic resin foam, the winding speed is increased in accordance with the expansion rate in the longitudinal direction due to foaming, compared with the feeding speed of the expandable thermoplastic resin sheet, and the thermoplastic resin is expanded according to the expansion in the width direction. The foam is widened in the width direction, thereby reducing wrinkles in the thermoplastic resin foam finally obtained.

However, this method requires complicated jigs and steps to expand the thermoplastic resin foam continuously produced during heating and foaming in the width direction.
In addition, since it is necessary to expand the thermoplastic resin foam after foaming and before cooling, the quality has to be reduced at both ends in the width direction of the obtained thermoplastic resin foam. As a result, in the obtained thermoplastic resin foam, it is necessary to remove portions in the vicinity of both ends in the width direction, so that there is a problem that productivity of the thermoplastic resin foam is reduced.

Further, the expandable thermoplastic resin sheet used in the above-mentioned manufacturing method is a sheet having a substantially uniform thickness because of the necessity of imparting tension in the longitudinal direction and the width direction in order to cope with expansion and expansion. It is necessary to form a thermoplastic resin foam from a continuous foamable thermoplastic resin sheet.Thus, the thermoplastic resin foam has excellent thickness accuracy, weight accuracy, and surface smoothness. Since it is a thermoplastic resin foam, there is a problem that it lacks compressive strength.

[0008] In order to solve this problem, if a deformed sheet is used, wrinkles are generated in the foam. Therefore, the obtained thermoplastic foam is limited to a flat plate shape, and a post-process of deforming the flat thermoplastic resin foam into an uneven shape is required to produce a thermoplastic resin foam having irregularities,
There was also a problem that productivity dropped.

On the other hand, JP-A-7-16856 discloses that
Pellets or cyclic materials (hereinafter abbreviated as “pellets”) made of a foaming thermoplastic resin containing a foaming agent are sprayed on a conveyor belt, and the foaming thermoplastic resin pellets and the like are foamed and expanded by heating. A method for obtaining a sheet-like thermoplastic resin foam by fusing and integrating the sheet is disclosed.

In this method, foamable thermoplastic resin pellets or the like are sprayed on a conveyor belt, the upper part of the conveyor belt is regulated in advance by a thermoplastic resin sheet or another conveyor belt, and the lower conveyor belt and the thermoplastic resin sheet are regulated. Alternatively, a thermoplastic resin foam having a desired thickness is formed by heating and foaming a thermoplastic resin pellet or the like with a lower conveyor belt, and the foamable thermoplastic resin is formed in the in-plane direction of the sheet. By filling the space between the pellets and the like with the expansion of the foamable thermoplastic resin pellets and the like, a sheet-like thermoplastic resin foam is obtained.

Also in this method, foamable thermoplastic resin pellets and the like expand three-dimensionally during foaming. However, the expandable thermoplastic resin pellets and the like are two-dimensionally discontinuously arranged on the conveyor belt, and the space between the expandable thermoplastic resin pellets is two-dimensional such as the expandable thermoplastic resin pellet. Filled by expansion. That is, since the foam is obtained by foaming the foamable thermoplastic resin in a pseudo one-dimensional foam form in the thickness direction, it is not necessary to expand or stretch in the width direction or the longitudinal direction, and the uneven thermoplastic resin is directly formed. There is a possibility that a resin foam can be obtained.

However, in this method, in order to perform foaming in the form of pseudo one-dimensional foaming, it is necessary to previously set a space corresponding to the expansion caused by foaming. It is necessary to control the dispersion state of the plastic resin pellets and the like with extremely high precision. That is, if the space corresponding to the expansion caused by foaming is too large, the foamable thermoplastic resin pellets and the like that are not continuous are foamed and expanded by heating and fused and integrated to obtain a sheet-like thermoplastic resin foam. There is a possibility that a portion that is not completely fused and integrated may occur, and if the space corresponding to the expansion caused by foaming is small, an uneven thermoplastic resin foam cannot be obtained, and a flat thermoplastic resin foam Becomes If the space is too small, pseudo one-dimensional foaming cannot be performed, and the surface smoothness of the foam decreases.

Therefore, a spraying device for spraying foaming thermoplastic resin pellets or the like with very high accuracy is required, and it is difficult to design irregularities of an arbitrary shape. It is not suitable as a method. In addition, if the thickness of the target thermoplastic resin foam is increased, the dimensions of the expandable thermoplastic resin pellets to be used must be increased, in which case the large pellets are heated uniformly. Need to
Since foaming takes time, productivity tends to decrease.

The foamed thermoplastic resin obtained by the above-mentioned method has a low foaming ratio skin layer formed on the surface of each foamable thermoplastic resin pellet at the time of foaming. Since a high foam made of a thermoplastic resin whose entire outer peripheral surface is coated on a thin film is a thermoplastic resin foam which is thermally fused through the low foam thin film, it has a high compressive strength, but has a high foaming thermoplastic resin. The quality of the obtained foam, such as thickness accuracy, weight accuracy, surface smoothness, and the like, is likely to be affected by the distribution of the pellets and the like, and there is a problem in that the dispersion of the compressive strength increases.

[0015]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and has a small variation in thickness accuracy and weight accuracy, a high cushioning property and a compressive strength, and a small variation in strength. And a method for producing the thermoplastic resin foam with high productivity.

[0016]

According to a first aspect of the present invention, there is provided a continuous foamed layer made of a thermoplastic resin, and a plurality of highly foamed portions made of a thermoplastic resin disposed on at least one surface of the continuous foamed layer. A low-foaming thin film made of a thermoplastic resin covering the outer surface of the high-foaming portion together with the continuous foaming layer, and a plate-like body made of a thermoplastic resin foam, the foam being orthogonal to the thickness direction. When projected on the projection surface, only the continuous foam layer, or a continuous surface on which only the continuous foam layer and the low foam thin film are projected, and a discontinuous surface on which the continuous foam layer, the low foam thin film and the high foam portion are projected In this case, at least one surface of the foam corresponding to the discontinuous surface is formed in a convex shape with respect to the portion of the foam corresponding to the continuous surface.

According to a second aspect of the present invention, there is provided a continuous foamed layer made of a thermoplastic resin, a high foamed portion made of a thermoplastic resin disposed on at least one side of the continuous foamed layer, and the continuous foamed layer. A plate-shaped body made of a thermoplastic resin foam having a low-foamed thin film made of a thermoplastic resin covering the outer surface of the high-foamed portion, when the foam is projected on a projection surface orthogonal to the thickness direction. A continuous surface on which only the continuous foamed layer or the continuous foamed layer and the low-foamed thin film are projected; and a discontinuous surface on which the continuous foamed layer, the low-foamed thin film and the high-foamed portion are projected. Is characterized in that at least one surface is formed in a convex shape and the other surface is formed in a concave shape with respect to the foam portion corresponding to the continuous surface.

In the first and second aspects of the present invention, the term "projection" refers to a shadow generated when a parallel light beam is irradiated from a direction perpendicular to a projection plane, and is a shadow generated by an interface between layers regardless of transparency or opacity. Say.

In the thermoplastic resin foam according to the first or second aspect of the present invention, preferably, as described in the third aspect, the plurality of high-foamed portions made of the thermoplastic resin are formed in a lattice shape. They are arranged or arranged in a staggered manner as described in claim 4.

Preferably, in the thermoplastic resin foam according to the first to fourth aspects of the present invention, the height of the convex portion of the highly foamed portion is 1 m with respect to the continuous surface.
m or more.

More preferably, in the thermoplastic resin foam according to the first to fifth aspects of the present invention, the volume of the thermoplastic resin foam is smaller than the volume of the smallest rectangular parallelepiped that can circumscribe the thermoplastic resin foam. (The ratio is hereinafter referred to as “filling ratio”).

More preferably, in the thermoplastic resin foam according to the first to sixth aspects of the present invention, the plurality of high foaming portions are heat-sealed to each other via a low foaming thin film.

The invention described in claim 8 provides a method for easily producing the thermoplastic resin foam of the present invention, wherein the foamable thermoplastic resin granules containing a foaming agent are planar. Are arranged substantially uniformly, and the expandable thermoplastic resin sheet-like body in which the expandable thermoplastic resin particles are integrally connected via an expandable thermoplastic resin thin film,
Heating and foaming above the decomposition temperature of the foaming agent,
Cooling in a cooling mold having voids more than the foam obtained by foaming is completely filled, thereby forming irregularities.

[Thermoplastic resin foam] The thermoplastic resin foam according to any one of the first to seventh aspects of the present invention is provided with a continuous foam layer made of a thermoplastic resin and a plurality of the foams disposed on at least one surface of the continuous foam layer. A highly foamed portion made of a thermoplastic resin,
A plate-like body made of a thermoplastic resin foam having a low-foaming thin film made of a thermoplastic resin covering the outer surface of the high-foaming portion together with the continuous foaming layer, wherein the foam is projected in a direction orthogonal to the thickness direction. When projected onto a surface, only the continuous foam layer, or a continuous surface on which only the continuous foam layer and the low foam thin film are projected,
A continuous foam layer, a low-foam thin film, and a discontinuous surface on which the high-foamed portion is projected, and a portion of the foam corresponding to the discontinuous surface is at least one of a portion of the foam corresponding to the continuous surface. Is formed in a convex shape.

Thermoplastic used for thermoplastic resin foam
The thermoplastic resin used for the continuous foamed layer, the low foamed thin film, and the high foamed portion constituting the thermoplastic resin foam according to the first to seventh aspects of the present invention is not particularly limited.
As such a thermoplastic resin, for example, low-density polyethylene, high-density polyethylene, linear low-density polyethylene (hereinafter, “polyethylene” refers to low-density polyethylene, high-density polyethylene, linear low-density polyethylene,
Or a mixture thereof. Olefin resins such as random polypropylene, homopolypropylene, block polypropylene (hereinafter, “polypropylene” refers to random polypropylene, homopolypropylene, block polypropylene, or a mixture thereof) and copolymers thereof; Polyethylene vinyl acetate, polyvinyl chloride, chlorinated polyvinyl chloride, ABS resin, polystyrene, polycarbonate, polyamide, polyvinylidene fluoride, pophenylene sulfide, polysulfone, polyether ketone, and copolymers thereof, and the like. May be used alone or in combination.

Among the above-mentioned thermoplastic resins, olefin resins such as polyethylene and polypropylene, which are easy to form irregularities, and mixtures thereof are preferable, and high-density polyethylene, homopolypropylene, or at least one of these, which can exhibit high compressive strength, is preferred. Mixtures containing are particularly preferred.

It is not necessary that the continuous foamed layer and the thermoplastic resin used for the low foamed thin film and the high foamed portion are the same resin. However, if the same type of resin is used, the fusion force of the thermoplastic resin foam can be improved. It is preferable to use the same type of resin because the resin is high and breakage during application of a compressive load hardly occurs.

The thermoplastic resin used for the low foamed thin film and the high foamed portion is preferably the same resin. The same resin is used when the thermoplastic resin sheet used in claim 8 described later is manufactured by foaming.

The thermoplastic resin used for the above-mentioned thermoplastic resin foam may be cross-linked, if necessary. The use of a cross-linked resin is effective in reducing the expansion ratio of the thermoplastic resin foam. This is preferable because the number of the components increases and the cushioning property and the lightness are improved.

In the case where the thermoplastic resin used in the thermoplastic resin foam is a mixture of a highly crosslinked thermoplastic resin and a low crosslinked or non-crosslinked thermoplastic resin having almost no compatibility with each other as described later, Low cross-linking resin composition can flow,
Highly foamed parts are easily heat-sealed with each other via the low foamed film,
When a load is applied to the obtained thermoplastic resin foam, it hardly breaks, which is preferable.

The thermoplastic resin used in the above-mentioned thermoplastic resin foam may, if necessary, be reinforced with short glass fibers, short carbon fibers, short polyester fibers, etc., in order to improve the compressive strength of the thermoplastic resin foam. Agents; fillers such as calcium carbonate, aluminum hydroxide, and glass powder may be added.

Shape of Thermoplastic Resin Foam The form of the thermoplastic resin foam of the present invention is such that when the foam is projected on a projection plane perpendicular to the thickness direction, only the continuous foam layer or the continuous foam layer and the low foam A continuous surface on which only the thin film is projected, a continuous foamed layer, a discontinuous surface on which the low-foaming thin film and the high-foamed portion are projected, and the discontinuous surface, and a foam corresponding to the discontinuous surface. The portion has at least one surface formed in a convex shape with respect to the portion of the foam corresponding to the continuous surface. In this case, it is preferable that the other surface of the portion of the foam corresponding to the discontinuous surface is formed in a concave shape because the cushioning property is further improved.

The expansion ratio of the thermoplastic resin foam is preferably from 2 to 30 times, more preferably from 3 to 20 because if it is too low, the lightness is impaired, and if it is too high, the compressive strength decreases.
And more preferably 5 to 10 times.

The thickness of the thermoplastic resin foam is 3 to 50 m
m is preferred, more preferably 3 to 30 mm, and still more preferably 5 to 20 mm.

If the foaming ratio of the low-foaming thin film is too low, the cushioning property of the thermoplastic resin foam decreases, and if it is too high, a thermoplastic resin foam having high compressive strength cannot be obtained. -10 times, more preferably 1.2 times
~ 7 times, more preferably 1.2 ~ 5 times.

If the thickness of the low-foamed thin film is too large, the weight of the thermoplastic resin foam cannot be reduced, and if it is too thin, a thermoplastic resin foam having high compressive strength cannot be obtained. 500 μm is preferred, and more preferably 40 μm.
To 400 μm, more preferably 50 to 400 μm. The thickness of the low-foaming thin film does not need to be uniform, and may be non-uniform. Here, the thickness of the low-foaming thin film refers to the average thickness of the low-foaming thin film in the cross-sectional direction of the thermoplastic resin foam.

The foaming ratio of the low foamed thin film is 1.1 to 10
When the thickness is 30 to 500 μm, the compressive strength and the weight reduction of the thermoplastic resin foam are both compatible, which is preferable, more preferably 1.2 to 7 times, and 40 to 400 μm, further preferably 1.2. Times to 5 times, 50 to 400 μm.

If the expansion ratio of the high-foamed portion is too low, it is difficult to reduce the weight, and if it is too high, a thermoplastic resin foam having high compressive strength cannot be obtained.
The ratio is preferably 5 times, more preferably 5 times to 50 times, and still more preferably 10 times to 35 times.

When the size of the highly foamed portion is too large, the compressive strength of the obtained thermoplastic resin foam decreases, and when it is too small, it becomes difficult to reduce the weight. Therefore, the size is preferably 3 to 50 mm. Preferably it is 5 to 30 mm. In addition,
The size of the highly foamed portion does not need to be uniform, and may be non-uniform. Here, the size of the highly foamed portion refers to the maximum value of the size in the cross-sectional direction.

If the expansion ratio of the continuous foam layer is too low, it is difficult to reduce the weight, and if it is too high, the fusion force decreases, and a thermoplastic resin foam having high compressive strength cannot be obtained. It is preferably 1 to 10 times, more preferably 2 to 8 times, and still more preferably 2 to 7 times.

If the thickness of the continuous foam layer is too large, the weight of the thermoplastic resin foam cannot be reduced, and if it is too thin, a thermoplastic resin foam having high compressive strength cannot be obtained. 5 mm is preferable, and more preferably 3 mm
00 μm to 3 mm, more preferably 500 μm to 2 m
m. The thickness of the continuous foam layer does not need to be uniform, and may be non-uniform. In addition, the continuous foam layer
It need not be a perfect flat plate, and may have some irregularities. Here, the thickness of the continuous foam layer refers to the average thickness of the continuous foam layer in the cross-sectional direction of the thermoplastic resin foam. When the thickness of the continuous foam layer is uneven or uneven, the projection plane refers to the maximum likelihood plane when the continuous foam layer is assumed to be completely flat.

The thermoplastic resin foam of the present invention is joined to a continuous foam layer, and a plurality of highly foamed portions having a low foamed thin film covering the outer surface except for a joint portion are formed by a low foamed thin film. The joining method is performed by heat fusion.

In order to improve the thickness accuracy and weight accuracy of the thermoplastic resin foam and reduce the variation in compressive strength, a plurality of high foams should be arranged substantially uniformly in a plane in the cross-sectional direction of the foam. Is preferred. However, the mode of arranging the plurality of high foams substantially uniformly in a plane is not particularly limited, and may be arranged in a lattice.
They may be arranged in a staggered manner.

When a plurality of high foams are arranged in a lattice, each high foam has a square pillar shape, and the surface smoothness of the thermoplastic resin foam is good and the compressive strength is sufficient. Therefore, the expandable thermoplastic resin particles are preferably arranged in a lattice shape.

When a plurality of high foams are arranged in a staggered manner, a structure in which a plurality of hexagonal column-shaped high foams are heat-sealed through a low-foaming thin film is formed. This is particularly preferable because a resin foam is obtained, and a thermoplastic resin foam having particularly excellent compressive strength is obtained.

The height of the protruding portion of the high foaming portion is preferably 1 mm or more, more preferably 2 mm, with respect to the continuous surface, because if the height is too low, a high cushioning property cannot be obtained.
It is more preferably 3 mm or more.

When the other surface of the foam portion corresponding to the discontinuous surface is formed in a concave shape, it is difficult to exhibit high compressive strength if the depth of the concave portion of the thermoplastic resin foam is too large. When it is too low, the effect of improving the buffering property cannot be obtained, so that the thickness is preferably 1 to 5 mm, more preferably 1 to 3 mm.

If the filling rate of the thermoplastic resin foam of the present invention is too large, high compressive strength cannot be exhibited, and if it is too small, the buffering property is reduced. ~ 90% is particularly preferred.

In order to improve the bending strength, the thermoplastic resin foam may be woven or non-woven with inorganic fibers such as glass paper or chopped strand mat, or woven with organic fibers such as polypropylene or polyester, if necessary. Cloth or nonwoven fabric; sheet made of thermoplastic resin or thermosetting resin; fiber reinforced thermoplastic resin sheet; sheet made of metal may be laminated.

[Method for Producing Thermoplastic Resin Foam] The method for producing the thermoplastic resin foam according to the first to seventh aspects of the present invention is not particularly limited. The thermoplastic resin pellets are foamed to form a plurality of high-foamed portions made of thermoplastic resin, which are covered with a low-foamed thin film made of thermoplastic resin on the outer surface excluding the fusion surface. After heat-sealing through a thin film, after heat-sealing a continuous foamed layer made of a thermoplastic resin formed in a separate step, a method of forming into a concavo-convex shape by a hot press or the like, for example, Foamable thermoplastic resin granules containing a foaming agent are arranged substantially uniformly in a plane, and the foamable thermoplastic resin granules are integrally connected via a foamable thermoplastic resin thin film. Expandable thermoplastic resin sheet , It said a step of blowing agent is heated to a temperature higher than the decomposition temperature of the foaming process and a step of cooling in the cooling mold foam obtained by foaming has more voids are completely filled is most preferred.

In the method for producing a thermoplastic resin foam according to the present invention, the foamable thermoplastic resin granules containing a foaming agent are arranged substantially uniformly in a plane, and A step of heating and foaming the foamable thermoplastic resin sheet body in which the thermoplastic thermoplastic granules are integrally connected via a foamable thermoplastic resin thin film at or above the decomposition temperature of the foaming agent; And forming the unevenness by cooling in a cooling mold having voids larger than or equal to the foam completely filled.

When the foamable thermoplastic resin sheet is foamed, a portion of the foamable thermoplastic resin granule foams.
At this time, since the outer surface of the thermoplastic resin particles hardly retains bubbles generated by foaming, the foaming ratio becomes lower than that of the inside, resulting in a low foamed thin film. As a result, the outer surface of the high foaming portion having a high foaming ratio inside the granular material is covered with the low foaming thin film. Further, the foamable thermoplastic resin thin film connecting the granules of the foamable thermoplastic resin sheet becomes a continuous foam layer, and a plurality of high foam portions are arranged on the continuous foam layer. Note that the continuous foam layer also has a small thickness, and it is difficult to hold air bubbles, so that low foaming occurs. Such a low-foaming thin film is closely fused with the low-foaming thin film of an adjacent granular material due to foaming inside the granular material. If the setting is made so that the plastic resin sheet is completely filled, the fusion proceeds only partially, and an uneven thermoplastic resin foam that is not completely filled can be obtained.

Used for a foamable thermoplastic resin sheet.
As the thermoplastic resin used for the expandable thermoplastic resin granules and the expandable thermoplastic resin thin film constituting the expandable thermoplastic resin sheet, the foamable thermoplastic resin is particularly preferable. There is no limitation, and the same thermoplastic resins as those described for the resin constituting the thermoplastic resin foam may be used.

The thermoplastic resin used for the foamable thermoplastic resin granules and the thermoplastic resin used for the foamable thermoplastic resin thin film do not need to be the same resin. From the viewpoint of the above, it is preferable to use the same type of resin.

The thermoplastic resin used for the foamable thermoplastic resin sheet may be cross-linked if necessary. It is preferable to use a crosslinked thermoplastic resin because the use of the crosslinked thermoplastic resin can improve the expansion ratio and reduce the weight of the obtained uneven thermoplastic resin foam. The crosslinking method is not particularly limited, for example,
1) A method in which a silane graft polymer is melt-kneaded with a thermoplastic resin, followed by water treatment and crosslinking. 2) A peroxide is melt-kneaded with the thermoplastic resin at a temperature lower than the decomposition temperature of the peroxide. A method of crosslinking by heating to a temperature equal to or higher than the decomposition temperature of the oxide, and 3) a method of crosslinking by irradiating radiation.

The crosslinking method using the silane graft polymer of the above 1) will be described. The silane-grafted polymer is not particularly limited, and examples thereof include silane-grafted polyethylene and silane-grafted polypropylene. The silane graft polymer can be obtained by, for example, graft-modifying the polymer with an unsaturated silane compound.

The unsaturated silane compound is represented by the general formula R ¹
Refers to a compound represented by SiR ² _m Y _3-m . Here, m is 0, 1, or 2. In the formula, R ¹ is an alkenyl group such as a vinyl group, an allyl group, a propenyl group, a cyclohexenyl group; a glycidyl group; an amino group; a methacryl group;
Organic functional groups such as halogenated alkyl groups such as chloroethyl group and γ-bromoethyl group.

In the formula, R ² represents an aliphatic saturated hydrocarbon group or an aromatic hydrocarbon group, for example, a methyl group, an ethyl group,
Examples thereof include a propyl group, a decyl group, and a phenyl group. In the formula, Y represents a hydrolyzable organic functional group, for example, a methoxy group, an ethoxy group, a formyloxy group, an acetoxy group, a propionoxyarylamino group, and the like.
Is 0 or 1, Y may be the same or different.

To increase the rate of the crosslinking reaction, the above unsaturated
As the silane compound, the general formula CH _Two= CHSi (O
A)_ThreeIs preferably represented by Wherein A is preferably
Is a fatty acid having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms.
It is an aliphatic saturated hydrocarbon group. CH _Two= CHSi (OA)_Three
Examples of preferred unsaturated silane compounds represented by
For example, vinyl trimethoxysilane, vinyl triethoxy
Orchid and vinyltriacetoxysilane.

As the method for producing the silane graft polymer, a general production method is used and is not particularly limited. For example, the above R ¹ SiR ² Y is added to polyethylene.
_A method of reacting an unsaturated silane compound represented by _3-m and an organic peroxide to obtain a silane-modified polyethylene.

For example, when Y is a methoxy group, the above silane graft polymer having a silyl group is hydrolyzed to a hydroxyl group by contact with water,
Hydroxyl groups of different molecules react with each other to form a Si—O—Si bond, and the silane graft polymers are crosslinked.

The method of mixing the silane graft polymer is as follows:
There is no particular limitation on the method as long as it can be uniformly mixed. For example, a method in which a thermoplastic resin and a silane graft polymer are supplied to a single-screw or twin-screw extruder and melt-kneaded, a method of melt-kneading using a roll, a method of melt-kneading using a kneader, and the like are exemplified.

The water treatment method described above includes a method of immersion in water and a method of exposure to water vapor.
When the treatment is performed at a temperature higher than 00 ° C., the treatment may be performed under pressure.

If the temperature of water and water vapor in the above water treatment is low, the rate of the crosslinking reaction decreases, and if the temperature is too high, the foamable thermoplastic resin sheet sticks to the heat.
50-130 ° C is preferred, and more preferably 90-12 ° C.
0 ° C. In addition, if the time for water treatment is short, the crosslinking reaction may not proceed completely, so the water treatment time is preferably set in the range of 0.5 to 12 hours.

If the addition amount of the silane graft polymer is too large, crosslinking is excessively performed, and the expansion ratio of the obtained irregular thermoplastic resin foam is reduced. If the addition amount is too small, cells are broken and uniform foam is formed. Since foam cells cannot be obtained, the addition amount of the silane graft polymer is preferably 5 to 50 parts by weight, more preferably 2 to 50 parts by weight, based on 100 parts by weight of the thermoplastic resin.
0 to 35 parts by weight.

When silane crosslinking is performed using a silane graft polymer, a silane crosslinking catalyst may be used if necessary. The silane crosslinking catalyst is not particularly limited as long as it promotes a crosslinking reaction between the silane graft polymers.For example, dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, tin octoate,
Examples include tin oleate, lead octane, zinc 2-ethylhexanoate, cobalt octoate, lead naphthenate, zinc cabrate, and zinc stearate.

When the addition amount of the silane crosslinking catalyst increases, the expansion ratio of the obtained irregular thermoplastic resin foam decreases, and when the addition amount decreases, the crosslinking reaction speed decreases and time is required for water treatment. The amount of the silane crosslinking catalyst added is 0.001 to 100 parts by weight of the thermoplastic resin.
A range of 10 parts by weight is preferred, more preferably 0.01 to
0.1 parts by weight.

The method 2) for crosslinking a thermoplastic resin with the above-mentioned peroxide will be described. The peroxide used in the present method is not particularly limited, and includes, for example, dibutyl peroxide, dicumyl peroxide, tert-butyl cumyl peroxide, diisopropyl peroxide, and the like. Mil peroxide and tertiary butyl cumyl peroxide are preferred, and dicumyl peroxide is particularly preferred.

If the amount of the peroxide is too large, the decomposition reaction of the resin tends to proceed, and the resulting irregular thermoplastic resin foam is colored. If the amount is too small, the crosslinking of the thermoplastic resin is not successful. In some cases, thermoplastic resin 1
The amount of the peroxide is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight.

The method 3) of irradiating radiation to crosslink the thermoplastic resin will be described. If the irradiation amount of the radiation is too large, crosslinking is excessively applied, and the expansion ratio of the obtained irregular thermoplastic resin foam is reduced.If the amount is too small, the foamed cells are broken, and uniform foamed cells cannot be obtained. Therefore, the radiation dose is preferably 1 to 20 Mrad, more preferably 3 to 10 Mrad.

The method of irradiating radiation is not particularly limited. For example, a method of using two electron beam generators, passing a thermoplastic resin sheet between them, and irradiating the thermoplastic resin with an electron beam. Is mentioned.

The foamable thermoplastic resin is not particularly limited as described above, but comprises a mixture of a foaming agent, a highly crosslinked thermoplastic resin having little compatibility with each other, and a low crosslinked or non-crosslinked thermoplastic resin. In this case, since the low-crosslinking or non-crosslinking resin easily flows at the time of foaming, the uneven portion of the obtained uneven thermoplastic resin foam is easily formed, which is particularly preferable.

The terms “highly crosslinked” and “lowly crosslinked” in the highly crosslinked thermoplastic resin and the lowly crosslinked or non-crosslinked thermoplastic resin are relative expressions determined by the magnitude of the degree of crosslinking of both, and the relative A highly crosslinked thermoplastic resin is referred to as a highly crosslinked thermoplastic resin, and the other is referred to as a low crosslinked or non-crosslinked thermoplastic resin.

As the thermoplastic resin (before crosslinking) used for the two types of thermoplastic resins having almost no compatibility with each other, two types of the thermoplastic resins described above (hereinafter referred to as crosslinking performance of the resin itself) are used. Rather, a resin that forms a highly crosslinked thermoplastic resin is referred to as a “highly crosslinkable resin”, and a resin that forms a low crosslinked or non-crosslinked thermoplastic resin is referred to as a “low (no) crosslinked resin”. Although it is possible, in order to uniformly and finely disperse the highly crosslinked thermoplastic resin and the low crosslinked or non-crosslinked thermoplastic resin without being compatible with each other, the thermoplastic resin of the highly crosslinked resin and the low (non) crosslinked resin is used. The difference in solubility parameter is preferably from 0.1 to 2.0, and more preferably from 0.2 to 1.5.

If the difference in the solubility parameter exceeds 2.0, the highly crosslinked thermoplastic resin obtained by crosslinking and the low crosslinked or non-crosslinked thermoplastic resin are very coarsely dispersed.
The expansion ratio of the obtained uneven thermoplastic resin foam decreases. On the other hand, if the difference in the solubility parameter is less than 0.1, the compatibility of the highly crosslinked thermoplastic resin obtained by crosslinking and the low crosslinked or non-crosslinked thermoplastic resin becomes high, and the obtained uneven thermoplastic resin foam is obtained. Has a reduced surface smoothness.

The solubility parameter is σ = ρΣFi
/ M. Here, ρ is the density of the resin component, M is the molecular weight of the monomer constituting the resin component, Fi
Is the number of moles of the monomer group.

When the difference in the melt index (MI) between the highly crosslinkable resin and the low (non) crosslinkable resin becomes large, the high crosslinkable thermoplastic resin obtained by crosslinking and the low crosslinkable or noncrosslinkable thermoplastic resin become Because it is very coarsely dispersed, the expansion ratio of the obtained uneven thermoplastic resin foam is reduced and becomes smaller, and the compatibility of the highly crosslinked thermoplastic resin obtained by crosslinking and the low crosslinked or non-crosslinked thermoplastic resin is high. Because it may be difficult to form the irregularities of the resulting irregular thermoplastic resin foam, the highly crosslinked thermoplastic resin and the low crosslinked or non-crosslinked thermoplastic resin are finely divided without being compatible with each other. In order to obtain a thermoplastic resin foam having a high expansion ratio and a high expansion ratio, the MI difference is 5 to 13 g / 1.
0 minutes is preferable, and 7-11 g / 10 minutes is more preferable.

Note that MI in this specification refers to JIS
It is a value measured according to K7210. In order to obtain a highly crosslinked thermoplastic resin obtained by crosslinking, a low crosslinked or non-crosslinked thermoplastic resin is uniformly and finely dispersed, and to obtain a thermoplastic resin foam having a high expansion ratio with excellent surface smoothness,
The mixing ratio between the highly crosslinkable resin and the low (non-) crosslinkable resin is desirably 2: 8 to 8: 2 by weight, and 4: 6.
~ 6: 4 is more preferable.

If the degree of cross-linking of the highly cross-linked thermoplastic resin is too high, cross-linking is excessively applied, and the expansion ratio of the obtained irregular thermoplastic resin foam decreases. Conversely, if it is too low, the cells break during foaming. Since a uniform cell may not be obtained,
The gel fraction serving as an index of the degree of crosslinking is preferably 5 to 40% by weight, more preferably 10 to 30% by weight.

If the degree of crosslinking of the low-crosslinking or non-crosslinking thermoplastic resin is too high, crosslinking may be excessive, and the fluidity of the resulting irregular thermoplastic resin foam may decrease, making it difficult to form irregularities. 5% by weight of gel fraction which is an indicator of the degree of crosslinking
Or less, more preferably 3% by weight or less.

The gel fraction in this specification refers to the percentage by weight of the residue weight after immersing the crosslinked resin component in xylene at 120 ° C. for 24 hours with respect to the weight of the crosslinked resin component before immersion in xylene.

As a method for preparing a mixture of a highly crosslinked thermoplastic resin and a low crosslinked or non-crosslinked thermoplastic resin having almost no compatibility with each other, the above two kinds of thermoplastic resins are mixed, and only the highly crosslinked resin is mixed. Or by cross-linking a highly crosslinkable resin preferentially over a low (no) crosslinkable resin.

Examples of a method of preferentially crosslinking a highly crosslinkable resin only or a highly crosslinkable resin over a low (non) crosslinkable resin include, for example, only a highly crosslinkable resin or a highly crosslinkable resin than a low (non) crosslinkable resin. A method of crosslinking using a crosslinking agent that preferentially crosslinks a resin. In the first step, a highly crosslinkable resin having a crosslinkable functional group is mixed with the same kind of crosslinkable resin to form a crosslinkable thermoplastic resin. Is formed, and in a second step, this is mixed with a non-crosslinkable resin.

It should be noted that the highly crosslinked thermoplastic resin and the low crosslinked or non-crosslinked thermoplastic resin can be uniformly and finely dispersed, that the highly crosslinked resin can be preferentially crosslinked, and that the thermoplastic resin can be easily prepared. From, having almost the same melt index as the highly crosslinkable resin, and having a crosslinkable functional group, after mixing the same type of crosslinkable resin with the high crosslinkable resin, together with the high crosslinkable resin and the low crosslinkable resin,
The method of crosslinking is most preferred.

The crosslinkable resin of the same type as the highly crosslinkable resin having a crosslinkable functional group having almost the same melt index as the highly crosslinkable resin may be a thermoplastic resin having a reactive functional group and capable of being crosslinked. It is not particularly limited. Examples of such a functional group include the above-described thermoplastic resins having an unsaturated group such as a vinyl group, an allyl group, and a propenyl group, a hydroxyl group, a carboxyl group, an epoxy group, an amino group, a silanol group, and a silanate group. Can be

Specific examples of the crosslinkable resin include maleic acid-modified polyethylene, maleic acid-modified polypropylene, silane-modified polyethylene, and silane-modified polypropylene. Silane-modified polyethylene and silane-modified polypropylene are the most preferred because it is easy to crosslink highly crosslinkable resin only with high crosslinkability resin or preferentially crosslink high crosslinkability resin than low (no) crosslinkability resin, and easy to crosslink after mixing. preferable.

If the difference in melt index between the highly crosslinkable resin and the crosslinkable resin is large, it becomes difficult to crosslink only the highly crosslinkable resin or to preferentially crosslink the highly crosslinkable resin over the low (no) crosslinkable resin. Melt index difference is 2
g / 10 minutes or less, preferably 1 g / 10 minutes or less.

Examples of the method of crosslinking the crosslinkable resin having a crosslinkable functional group include a method of crosslinking with a peroxide,
Examples of the method include a method of crosslinking with an isocyanate, a method of crosslinking with an amine, and a method of hydrolyzing a reactive functional group followed by water crosslinking.

The method of crosslinking with water after hydrolyzing the reactive functional group is most preferable because the crosslinking after mixing is easy.

Blowing agent In the eighth aspect of the present invention, a pyrolytic foaming agent is used as a blowing agent contained in the expandable thermoplastic resin granules and the expandable thermoplastic resin thin film.

The pyrolytic foaming agent is not particularly limited as long as it has a decomposition temperature higher than the melting temperature of the thermoplastic resin used. Examples thereof include sodium bicarbonate, ammonium carbonate, ammonium bicarbonate and azide. Compounds, inorganic pyrolytic blowing agents such as sodium borohydride; azodicarbonamide, azobisformamide, azobisisobutyronitrile, barium azodicarboxylate, diazoaminobenzene, N, N'-dinitrosopentamethylenetetramine , P-toluenesulfonyl hydrazide, P, P'-oxybisbenzenesulfonyl hydrazide, trihydrazinotriazine, etc., which are easy to adjust the decomposition temperature and decomposition rate, generate a large amount of gas, and are excellent in hygiene. Amides are preferred.

If the amount of the thermal decomposition type foaming agent is too large, bubbles may be broken and uniform cells may not be formed. On the other hand, if the amount is too small, foaming may not be sufficiently performed. It is preferable that the content be contained in a proportion of 1 to 25 parts by weight based on 100 parts by weight of the thermoplastic resin.

In order to increase the strength of the component foam which can be added , the above-mentioned thermoplastic resin used for the above-mentioned foamable thermoplastic resin granules and the foamable thermoplastic resin thin film may, if necessary, be made of glass. Reinforcing materials such as fibers, short carbon fibers, and short polyester fibers; fillers such as calcium carbonate, aluminum hydroxide, and glass powder may be added.

When the above-mentioned short fibers are added as a reinforcing material, if the addition ratio of the reinforcing material is too large, the cells are broken at the time of foaming, and a foam having a high expansion ratio cannot be obtained. In addition, the effect of reinforcing the obtained foam cannot be sufficiently obtained. Therefore, when the short fibers are added, the mixing ratio is preferably 1 to 20 parts by weight, particularly preferably 3 to 10 parts by weight, per 100 parts by weight of the thermoplastic resin.

If the length of the short fibers is too long, the cells are broken during foaming, and a foam having a high expansion ratio cannot be obtained. If the length is too short, the effect of reinforcing the obtained foam is sufficiently obtained. The length of the short fibers may be 1 to 20
mm is preferred, and 3-5 mm is particularly preferred.

In addition, when the above-mentioned filler is added, if the amount is large, the cells are broken at the time of foaming and a foam having a high expansion ratio cannot be obtained. If the amount is small, the obtained foam is reinforced. Effect may not be obtained sufficiently. Therefore, the addition amount of the filler is preferably 10 to 100 parts by weight, particularly preferably 30 to 50 parts by weight, based on 100 parts by weight of the thermoplastic resin.

[0097] The shape of expandable thermoplastic resin granular materials the expandable thermoplastic resin granular materials is not particularly limited, for example, hexagonal-shaped, cylindrical, although such spheroids and the like, expandable thermoplastic resin granular When the body foams, the column shape is most preferable in order to perform foaming uniformly.

When the expandable thermoplastic resin particles are cylindrical, the diameter thereof is not particularly limited because it varies depending on the expansion ratio, thickness, etc. of the target uneven thermoplastic resin foam. If it is too large, the foaming speed will be reduced, and if it is too small, the column will melt and deform due to heating during foaming, it will be easily deformed, and it will not be possible to express primary foaming, and the thickness accuracy and weight accuracy will have large variations. Therefore, when the expandable thermoplastic resin particles are cylindrical, the diameter is preferably 1 to 30 mm, and particularly preferably 2 to 20 mm.

When the expandable thermoplastic resin particles are cylindrical, the height thereof is not particularly limited because it varies depending on the expansion ratio and thickness of the target thermoplastic resin foam. If it is too high, the foaming speed will decrease, and if it is too low, it will foam simultaneously with the foamable thermoplastic resin thin film, so that it will expand greatly in the width direction and the longitudinal direction. Therefore, the height of the columnar foamable thermoplastic resin granules is 1 to 3
It is preferably 0 mm, more preferably 2 to 20 mm.

The distance between the expandable thermoplastic resin granules is not particularly limited since it varies depending on the expansion ratio, thickness, etc. of the target thermoplastic resin foam, but if the distance is too long. When the expandable thermoplastic resin granules foam, there is a possibility that a large amount of insufficient filling occurs. If the amount is too short, complete filling occurs. Therefore, the center-to-center distance between the expandable thermoplastic resin particles is preferably 2 to 50 mm, more preferably 3 to 30 mm.

In order to improve the thickness accuracy and weight accuracy of the finally obtained thermoplastic resin foam, and to make the unevenness and the expansion ratio uniform, the foamable thermoplastic resin granules are formed from the foamable thermoplastic resin. It is necessary to arrange the sheet-like body substantially uniformly in a plane. However, the mode in which the thermoplastic resin granules are arranged substantially uniformly in a plane is not particularly limited, and may be arranged in a lattice.
They may be arranged in a staggered manner. When the foamable thermoplastic resin granules are arranged in a lattice, the high foaming portions obtained by foaming the individual foamable thermoplastic resin granules have a square pillar shape, and the irregular thermoplastic resin foam is formed. The foamable thermoplastic resin granules are preferably arranged in a lattice shape so that the body has a uniform buffering property and a sufficient compressive strength.

Further, when the expandable thermoplastic resin particles are arranged in a staggered manner, the highly foamed portions obtained by foaming the individual expandable thermoplastic resin particles have a hexagonal column shape. Thus, a pseudo honeycomb structure is formed.
Therefore, the cushioning property of the obtained irregular thermoplastic resin foam becomes uniform, and the compressive strength becomes sufficient. Therefore,
Preferably, the foamable thermoplastic resin granules are arranged in a staggered manner.

[0103] expandable thermoplastic resin film expandable thermoplastic resin film of thickness is different depending on the expansion ratio and thickness, and the like of the thermoplastic resin foam of interest,
Although not particularly limited, if the thickness is too large, the expandable thermoplastic resin particles move during foaming, and the expansion in the width direction and the longitudinal direction increases.If the thickness is too thin, the expandable thermoplastic resin particles are held. become unable. Therefore, the thickness of the foamable thermoplastic resin thin film is preferably from 0.05 to 3 mm, more preferably from 0.1 to 2 mm.

Method for Producing a Foamable Thermoplastic Resin Sheet The method for producing the above foamable thermoplastic resin sheet is not particularly limited. For example, 1) constituting a foamable thermoplastic resin sheet The thermoplastic resin and the foaming agent are supplied to the injection molding machine, melt-kneaded at a temperature lower than the decomposition temperature of the pyrolytic foaming agent, and injected into a mold having a concave portion corresponding to the shape of the foamable thermoplastic resin granules. 2) The thermoplastic resin and the foaming agent constituting the foamable thermoplastic resin sheet are supplied to an extruder and cooled at a temperature lower than the decomposition temperature of the pyrolytic foaming agent. After melt-kneading, the sheet-like foamable thermoplastic resin in a softened state has a clearance smaller than the thickness of the sheet-like foamable thermoplastic resin, and a large number of recesses are uniformly arranged on at least one outer peripheral surface. Different Introduced to a pair of forming roll that rotates in direction, after the press-fitted portion of the sheet-shaped foamable thermoplastic resin softened state into the recess, cooling method for releasing being most preferred.

The method 2) will be described in more detail.
First, in order to obtain a sheet-shaped foamable thermoplastic resin in a softened state, a method of melt-kneading and extruding the foamable thermoplastic resin with an extruder or a method of melting using a calender roll is usually used. The melting used is most preferable from the viewpoint of continuous weight accuracy and quantitativeness.

The foamed thermoplastic resin in the softened state has the form
The form is not particularly limited as long as it can be continuously formed, and includes a sheet form, a large number of strand forms, and the like. The sheet form is most preferable from the viewpoint of quantitativeness in the direction perpendicular to the flow (width direction).

The recesses on the outer peripheral surface of the shaping roll are preferably arranged substantially uniformly in order to improve the weight accuracy and the thickness accuracy of the foamable thermoplastic resin sheet obtained.
The arrangement of the concave portions on the outer peripheral surface of the shaping roll is not particularly limited as long as it is uniform over the entire outer peripheral surface of the shaping roll, but since it is more uniform, it is most preferably arranged in a lattice or staggered manner. .

The shape of the concave portion on the outer peripheral surface of the shaping roll is not particularly limited, and examples thereof include a hexagonal shape, a columnar shape, a spherical shape, and the like. The column shape is most preferable because the body can be easily molded uniformly and the mold can be easily released after cooling.

When the shape of the concave portion on the outer peripheral surface of the shaping roll is cylindrical, the diameter of the cylindrical column is not particularly limited because it varies depending on the shape of the target foamable thermoplastic resin sheet, but is too large. And the mold release after cooling is difficult to perform, the foamable thermoplastic resin thin film is broken, and if too small, the foamable thermoplastic resin granules are broken at the time of mold release after cooling.
mm, more preferably 2 to 20 mm.

When the shape of the concave portion on the outer peripheral surface of the shaping roll is cylindrical, the height of the cylinder is not particularly limited because it varies depending on the shape of the target foamable thermoplastic resin sheet. If the temperature is too high, the mold release after cooling is difficult to perform, and the foamable thermoplastic resin thin film is broken. If the temperature is too low, a foamable thermoplastic resin sheet that can perform one-dimensional foaming cannot be formed. 2-20
mm.

The clearance of the shaping roll must be smaller than the thickness of the softened sheet-like foamable thermoplastic resin. Therefore, within this range, there is no particular limitation because the shape changes according to the shape of the target foamable thermoplastic resin sheet, but if it is too thick, a foamable thermoplastic resin sheet capable of performing one-dimensional foaming is formed. No longer,
If the thickness is too thin, the foamable thermoplastic resin thin film is easily broken at the time of release after cooling, so that the thickness is preferably 0.05 to 3 mm, more preferably 0.1 to 2 mm.

The method of press-fitting a part of the softened sheet-like foamable thermoplastic resin into the concave portion is performed by applying the pressure to the softened sheet-like foamable thermoplastic resin by keeping the clearance of the pair of shaping rolls unchanged. This is achieved by applying pressure from a form roll.

The method of cooling the partially formed sheet-shaped foamable thermoplastic resin in a softened state is not particularly limited as long as it can be lowered to the melting point of the foamable thermoplastic resin or lower. There are methods such as flowing cooling water inside the roll.

In the method according to the eighth aspect of the present invention, the foamable thermoplastic resin sheet is heated to a temperature not lower than the decomposition temperature of the foaming agent and foamed. Cooling is carried out by a cooling device having a gap larger than the plastic resin sheet is completely filled. In this case, for the step of foaming by heating, it is possible to use an appropriate method capable of heating the foamable thermoplastic resin sheet to a temperature equal to or higher than the decomposition temperature of the pyrolytic foaming agent contained in the foamable thermoplastic resin granules. Examples thereof include a method of heating using an electric heater, a far-infrared heater, a heating device that circulates a heating medium such as heated oil or air, or the like.

The cooling device for the thermoplastic resin foam is not particularly limited as long as it has a gap larger than the space where the thermoplastic resin sheet which expands and expands is completely filled, and the softening of the resin constituting the foam is performed. An appropriate method capable of cooling to a temperature equal to or lower than the point can be adopted.For example, a method of cooling using a cooling device or the like that circulates a cooling medium such as cooled water or air can be adopted. .

The gap beyond which the expandable thermoplastic resin sheet is completely filled is a size calculated from the expansion ratio, weight, etc. of the expandable thermoplastic resin sheet, but the gap is too large. And the entire thermoplastic resin foam is greatly wavy, so that it is 10 mm from the completely filled gap calculated from the expansion ratio, weight, etc. of the foamable thermoplastic resin sheet.
It is preferable that the width is equal to or less than 5 mm, more preferably 5 mm or less.
More preferably, it is 3 mm or less.

[0117]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an example of the thermoplastic resin foam according to the first or third aspect of the present invention.
FIG. 2 is a virtual projection view in which the thermoplastic resin foam of FIG. 1 is projected on a projection plane orthogonal to the thickness direction.

In FIG. 1, 1 is a thermoplastic resin foam, 2
Is a continuous foam layer, 3 is a high foam portion, and 4 is a low foam thin film.
As shown in FIG. 1, a thermoplastic resin foam 1 according to the first aspect of the present invention has a continuous foam layer 2 made of a thermoplastic resin, and a plurality of thermo foams arranged substantially uniformly on one surface of the continuous foam layer 2. It is a plate-shaped thermoplastic resin foam comprising a highly foamed portion 3 made of a thermoplastic resin and a low foamed thin film 4 made of a thermoplastic resin covering the outer surface of the highly foamed portion 3 together with the continuous foamed layer 2.

Further, as shown in FIG. 2, when the foam is projected on a projection surface orthogonal to the thickness direction, a continuous surface 5 formed by projecting only the continuous foam layer 2 and the low-foam thin film 4;
A discontinuous surface 7 formed by projecting only the continuous foam layer 2 and the low foam thin film 4, the continuous foam layer 2, the low foam thin film 4, and the high foam portion 3
Is formed by projecting the discontinuous surface 6, and a portion of the foam corresponding to the discontinuous surface 6 is formed to have a convex shape on one surface with respect to a portion of the foam corresponding to the continuous surface 5. (FIG. 1). The discontinuous surfaces 6 formed by projecting the highly foamed portions 3 are arranged in a substantially lattice shape.

That is, the plurality of high-foamed portions 3 having at least one surface formed in a convex shape are spaced apart from each other by a predetermined distance without being joined to the adjacent high-foamed body 3 via the low-foamed thin film 4 on the side surface. Are held apart, and the bottom in FIG. 1 is formed in a convex shape.

FIG. 3 is a cross-sectional view showing an example of the thermoplastic resin foam of the invention according to claim 7, and FIG. 4 is a virtual projection of the thermoplastic resin foam of FIG. 3 onto a projection plane orthogonal to the thickness direction. It is a projection view.

In FIG. 3, 31 is a thermoplastic resin foam,
32 is a continuous foam layer, 33 is a high foam part, and 34 is a low foam thin film. As shown in FIG. 3, the thermoplastic resin foam 31 according to the seventh aspect of the present invention includes a continuous foam layer 32 made of a thermoplastic resin, and a plurality of substantially uniform thermal foams disposed on one surface of the continuous foam layer 32. It is common to the thermoplastic resin foam 1 in that it comprises a high foaming portion 33 made of a thermoplastic resin and a low foaming thin film 34 made of a thermoplastic resin covering the outer surface of the high foaming portion 33 together with the continuous foaming layer 32. , A plurality of high foaming parts 33
Are different from the thermoplastic resin foam 1 in that they are plate-like bodies made of a thermoplastic resin foam which are thermally fused to each other via a low foaming thin film 34.

Further, as shown in FIG. 4, when the foam is projected on a projection surface orthogonal to the thickness direction, a continuous surface 3 formed by projecting only the continuous foam layer 32 and the low foam thin film 34 is formed.
5, a continuous foam layer 32, a low foam thin film 34, and a high foam section 33.
Is formed by projecting a discontinuous surface 36, and a portion of the foam corresponding to the discontinuous surface 36 is formed such that one surface thereof is convex with respect to a portion of the foam corresponding to the continuous surface 35. (FIG. 3). Further, the discontinuous surfaces 36 formed by projecting the high foaming portions 33 are arranged in a substantially lattice shape.

That is, the plurality of high-foamed portions 33 having at least one surface formed in a convex shape are portions of the side surfaces which are not joined to the adjacent high-foamed body 33 via the low-foamed thin film 34. Are formed in a more convex shape than the portion where they are joined.

FIG. 5 is a virtual projection view in which the thermoplastic resin foam according to the seventh aspect of the present invention is projected onto a projection plane orthogonal to the thickness direction. 3 is the same as FIG. 3 except that the discontinuous surfaces 16 on which the highly foamed portions are projected are arranged in a substantially lattice shape.

FIG. 6 is a cross-sectional view showing an example of the thermoplastic resin foam according to the seventh aspect of the present invention. In FIG. 6, 11 is a thermoplastic resin foam, 12 is a continuous foam layer, 13 is a high foam portion, and 14 is a low foam thin film.
The projection of the foam is the same as in FIGS. As shown in FIG. 6, the continuous surface 3 of FIGS.
For the foam parts corresponding to 5 and 15,
3 (corresponding to the discontinuous surfaces 36 and 16 in FIGS. 3 and 5) has one surface formed in a convex shape and the other surface formed in a concave shape.

FIG. 7 is a cross-sectional view for explaining a foaming step of the method for producing the thermoplastic resin foam of the invention according to the seventh aspect of the present invention by citing the second aspect.
FIG. 8 is a cross-sectional view illustrating the cooling step. FIG.
As shown in the above, in the method for producing a thermoplastic resin foam according to the invention of claim 8, first, foamable thermoplastic resin particles 25 containing a foaming agent are arranged substantially uniformly in a plane,
In addition, a foamable thermoplastic resin sheet 27 in which the foamable thermoplastic resin particles 25 are integrally connected via a foamable thermoplastic resin thin film 26 is disposed on a fluorinated ethylene resin sheet 28. Further, a fluorinated ethylene resin sheet 29 is superposed thereon, and is heated and foamed at a temperature higher than the decomposition temperature of the foaming agent.

At this time, first, only the foamable thermoplastic resin thin film 26 having a small heat capacity foams first, and the foamable thermoplastic resin particles 25 having a large heat capacity do not foam. For this reason,
The foamable thermoplastic resin thin film 26 hardly expands in the in-plane direction, and becomes the wavy continuous foam layer 12 shown in FIG. Further, gaps between the expandable thermoplastic resin particles 31 are filled to form the low-expandable thin film 14 shown in FIG. Thereafter, the expandable thermoplastic resin granules 25 are expanded, and the highly expanded portions 13 are formed.
When the thermoplastic resin foam 11 is cooled in the cooling molds 30 and 30 having voids equal to or more than completely filled, a convex portion is formed on the surface opposite to the concave portion.

[0129]

EXAMPLES The effects of the present invention will be clarified by giving non-limiting examples and comparative examples of the present invention.

Production of expandable thermoplastic resin sheet Examples 1 to 10 and Comparative Example 3 50 parts by weight of polypropylene (manufactured by Mitsubishi Yuka Co., Ltd., product number "MA-3"; melt index 11 g / 10 min), crosslinkability Silane-modified polypropylene (Mitsubishi Yuka Co., Ltd., product number "XP
M800H "; melt index 11 g / 10 min, gel fraction after crosslinking 80% by weight) 50 parts by weight, high-density polyethylene (Mitsubishi Yuka Co., product number"HY3405; melt index 1.5 g / 10 minutes) 20 parts by weight 0.1 part by weight of dibutyltin dilaurate as a silane crosslinking catalyst, and azodicarbonamide (manufactured by Otsuka Chemical Co., Ltd., product number “SO-20”, decomposition temperature 210 ° C.) 4 as a pyrolytic foaming agent
The parts by weight were supplied to the twin-screw extruder 21 shown in FIG. 2
The screw extruder 21 used had a diameter of 44 mm. 2
The composition was melt-kneaded at 180 ° C. in a screw extruder 21 and extruded into a softened sheet-like foamable thermoplastic resin by a T-die 22 having a surface length of 500 mm.

Furthermore, the diameter, 250 mm, and the surface length, 500 mm, having the cylindrical concave portions 23a arranged in correspondence with the arrangement, height, diameter, and center-to-center spacing between the granules shown in Table 1 were obtained.
Is cooled while shaping a softened sheet-like foamable thermoplastic resin between the shaping rolls 23 and 24, and a foaming agent containing a foaming agent is formed in a portion corresponding to the recess 23a of the shaping roll 23. The thermoplastic resin granules 25 are arranged substantially uniformly in a plane, and the foamable thermoplastic resin granules 2
5 was obtained as a foamable thermoplastic resin sheet 27 integrally connected via a foamable thermoplastic resin thin film 26.
The obtained foamable thermoplastic sheet 27 was immersed in water at 98 ° C. for 2 hours and then dried to obtain a foamable thermoplastic resin sheet having the form shown in Table 1.

The foamable thermoplastic resin particles 25 in the foamable thermoplastic resin sheet 27 obtained as described above.
Table 1 summarizes the arrangement, height, diameter, and center-to-center spacing between the granular materials, and the thickness of the foamable thermoplastic resin thin film 26.

The height of the expandable thermoplastic resin particles means the expandable thermoplastic resin thin film when the expandable thermoplastic resin thin film is connected to one end in the height direction of the expandable thermoplastic resin particles. It refers to the dimension in the height direction of the foamable thermoplastic resin granule not including the thickness of the resin thin film.

Production of thermoplastic resin foam The foamable thermoplastic resin sheet 2 obtained as described above
7 is placed on the fluorinated ethylene resin sheet 28 shown in FIG. 7 so as to have the weight shown in Table 1, and the fluorinated ethylene resin sheet 29 is further superimposed thereon. After heating and foaming for 30 minutes, it was transferred to a cooling press mold 30 at 30 ° C. having the gaps shown in Table 1,
After cooling for 10 minutes, a thermoplastic resin foam was obtained.

Comparative Example 1 A sheet extruded from a T-die was cooled by passing between rolls having a diameter of 250 mm and a surface length of 500 mm without concave portions on the surface, and the cooled sheet was immersed in 98 ° C. water for 2 hours and then dried. Except that a flat foamable thermoplastic resin sheet having a thickness of 1.0 mm was obtained, and that the foamable thermoplastic resin sheet was disposed on a sheet made of fluorinated ethylene resin so as to have the weight shown in Table 1. In the same manner as in Example 1, a thermoplastic resin foam was obtained. The obtained thermoplastic resin foam was sized to have a depth of 3 mm, a diameter of 10 mm, a center-to-center distance of 10.1 mm, and a large number of staggered holes on one surface.
0 × 200 × with closed mold 800 g / m ² filling of 5 mm, temperature 170 ° C., were thermally shaping under a pressure of 0.5 kgf / cm ^2, were molded evaluation samples shown in Table 1.

Comparative Example 2 A sheet extruded from a T-die was cooled between rolls having no concave portions on the surface and having a diameter of 250 mm and a surface length of 500 mm, and then pelletized.
After soaking for an hour, it was dried. Thus, 5 × 5 mm
A foamable thermoplastic resin pellet having a thickness of 1.5 mm was obtained. A thermoplastic resin foam was obtained in the same manner as in Comparative Example 1 except that the obtained foamable thermoplastic resin pellets were sprayed on a sheet made of a fluoroethylene resin so as to have a weight shown in Table 1.

The thickness, expansion ratio and pseudo one-dimensional expandability of the obtained thermoplastic resin foam were measured. The results are shown in Table 1.

(Thickness of Foam) Using a caliper, the thickness of the obtained thermoplastic resin foam was measured. (Expansion Ratio) The expansion ratio of the obtained thermoplastic resin foam was measured by an underwater substitution method. (Pseudo one-dimensional foamability) Measure the area of the foamable thermoplastic resin sheet placed before foaming and the area of the obtained irregular thermoplastic resin foam, and determine the ratio of the latter to the former,
Pseudo one-dimensional foaming. The closer this value is to 1, the higher the pseudo one-dimensional foamability.

[0139]

[Table 1]

Preparation of Evaluation Samples Examples 1, 3, 5, 7, 9 The concave surface of the obtained thermoplastic resin foam was cut with a sander so that the thickness of the thermoplastic resin foam became 8 mm.

Examples 2, 4, 6, 8, 10 and Comparative Examples 1 to
3 The obtained thermoplastic resin foam was used for evaluation as it was.

The thickness, expansion ratio, presence or absence of concave portions, height of convex portions, and filling ratio of the obtained thermoplastic resin foam were measured as follows. The results are shown in Table 2.

(Presence or absence of concave portion) The presence or absence of a concave portion having a depth of 1 mm or more was visually evaluated. (Protrusion height) The thickness of the non-fused portion of the high-foamed material whose outer surface is covered with a low-foaming thin film that has been cut in the longitudinal section direction of the thermoplastic resin foam and has not been fused. The maximum value in the vertical direction was measured with a caliper. (Filling rate) Volume (true volume) obtained by dividing the weight of the thermoplastic resin foam by the density in the volume (bulk volume) obtained from the maximum height when the thermoplastic resin foam is placed on a flat plate. Was determined.

The presence or absence of concave portions, the height of convex portions, and the filling factor of the obtained thermoplastic resin foam were measured in the same manner as in the examples. The results are shown in Table 2.

The thickness variation, the amount of compression deformation variation, and the maximum impact force of the obtained thermoplastic resin foam were measured as follows. The results are shown in Table 2 below.

(Variation in Thickness) The thickness of the foam at n = 20 was measured using calipers, and the difference between the maximum value and the minimum value was determined. (Compression deformation amount) By cutting, 200mm x 200mm
Of foam and a thickness of 3 m on the surface opposite to the convex surface of the foam.
After bonding the plywood of m, a compression test was performed with a φ50 mm cylindrical indenter and a holding speed of 2 m / min, and the amount of compressive deformation under a load of 80 kgf was defined as the amount of sinking. At this time, n = 2
The thickness of the foam having a thickness of 0 was measured for compressive deformation, and the difference between the maximum value and the minimum value was determined, which was taken as the variation in the amount of compressive deformation. (Maximum impact force) By cutting, 200mm x 200mm
Of foam and a thickness of 3 m on the surface opposite to the convex surface of the foam.
After bonding the plywood of JIS m, JIS from the height of 40mm
The maximum impact force when the hammer defined by A1418 was dropped was measured by an acceleration sensor.

[0147]

[Table 2]

As is clear from Table 1, the thermoplastic resin foam obtained in Comparative Example 1 was able to obtain an irregular thermoplastic resin foam having an expansion ratio of 8 times. Was extremely large at 4.00, and therefore expanded considerably during foaming also in the length and width directions. Further, the thermoplastic resin foam is wavy, and the thickness variation is very large. In addition, since the thermoplastic resin foam was homogeneous, the compressive strength was low and the sink amount was 2.2 mm, which was a very large value.

Further, in Comparative Example 2, a thermoplastic resin foam having an expansion ratio of 8 was obtained by using foamable thermoplastic resin pellets. Although the pseudo one-dimensional foamability is smaller than that of Comparative Example 1 due to a gap between the foamable thermoplastic resin pellets, it is slightly higher than 1.25 because it depends on the spraying accuracy of the foamable thermoplastic resin pellets. Therefore, it was recognized that the swelling occurred at a considerable rate also in the width direction and the longitudinal direction. As a result, the variation in the thickness became a large value. Although the compressive strength of the obtained thermoplastic resin foam is slightly larger than that of Comparative Example 1 due to the formation of a low-foaming thin film, the amount of compressive deformation is as large as 1.75 mm and the variation is very large. Value.

In Comparative Example 3, a three-dimensionally uniform thermoplastic resin foam having an expansion ratio of 8 was obtained by using the foamable thermoplastic resin sheet. Thermoplastic foam 3
Since it is dimensionally uniform, the amount of compressive deformation is 1.75 mm ²
And small variation, but the filling rate is 100%
Since the thermoplastic resin foam was a flat thermoplastic resin foam, the maximum impact force was large and sufficient cushioning property could not be exhibited.

On the other hand, in the thermoplastic resin foams obtained in Examples 1 to 7, a low foamed thin film was formed.
Since the amount of compressive deformation was as small as 1.4 mm or less and the dispersion was small, it was also found that the foam was an irregular thermoplastic resin foam having high compressive strength. In addition, since the buffering performance was equal to or higher than that of Comparative Example 1 having a small compressive strength, a thermoplastic resin foam having both compressive strength and buffering properties was obtained.

Examples 1, 2, and 3, 4 and 5,
From the comparison between Nos. 6, the thermoplastic resin foam having the concave portions was a thermoplastic resin foam having a reduced maximum impact force and an excellent cushioning property.

Further, in Examples 1, 3, and 5, and in Example 2,
From the comparison between 4 and 6, the thermoplastic resin foam which is superior in both compressive strength and buffering property when arranged in a lattice is better than when foamable thermoplastic resin particles are arranged almost uniformly at random. Thus, a thermoplastic resin foam having the most excellent compressive strength when it was arranged in a staggered manner was obtained.

From the comparison with Examples 5 to 10, it was found that a particularly high buffering property can be exhibited when the height of the convex portion is 3 mm or more. Strength and cushioning can be compatible.

[0155]

The uneven thermoplastic resin foam according to the first aspect of the present invention comprises a continuous foam layer made of a thermoplastic resin and a plurality of thermoplastic resins arranged on at least one surface of the continuous foam layer. And a plate-shaped body made of a thermoplastic resin foam having a low-foamed thin film made of a thermoplastic resin covering the outer surface of the high-foamed portion together with the continuous foamed layer. When projected on a projection plane orthogonal to the thickness direction, only the continuous foam layer, or a continuous face on which only the continuous foam layer and the low foam thin film are projected, and the continuous foam layer, the low foam thin film, and the high foam portion are projected. Consisting of a discontinuous surface, the portion of the foam corresponding to the discontinuous surface, the portion of the foam corresponding to the continuous surface, at least one surface is formed in a convex shape, the variation is small , High compressive strength can be developed. In addition, since the high-foamed body whose outer surface is covered with the low-foaming thin film is formed on at least one surface in a convex shape, the shock-absorbing property is excellent.

According to the second aspect of the present invention, since the high-foamed material whose outer surface is covered with the low-foaming thin film is formed on one surface in a convex shape and on the other surface in a concave shape, The buffer performance is further improved, and the decrease in compressive strength is small.

According to the third aspect of the present invention, the high-foamed bodies are arranged in a lattice, each high-foamed body is in the shape of a square pillar, and the thickness variation of the thermoplastic resin foam is small. Both compressive strength and cushioning property are improved.

According to the fourth aspect of the present invention, the high foams are staggered, and a plurality of hexagonal column-shaped high foams are heat-sealed through the low foam thin film. As a whole, it becomes a honeycomb-shaped thermoplastic resin foam. Therefore, a thermoplastic resin foam having particularly excellent compressive strength is obtained.

According to the fifth aspect of the present invention, since the height of the convex portion is 1 mm or more, the uneven thermoplastic resin foam having excellent buffer performance is obtained.

According to the sixth aspect of the present invention, since the filling rate is 50 to 90%, the foam is excellent in compressive strength and high in cushioning property.

According to the invention of claim 7, according to claim 1,
In addition to the configuration described above, since the continuous foamed layer is thermally fused so as to connect the individual high foamed materials, there is no peeling or breakage at the fusion interface between the low foamed thin films when a compression load is applied.

According to the method for producing a thermoplastic resin foam according to the eighth aspect of the present invention, the foamable thermoplastic resin granules containing a foaming agent are substantially uniformly arranged in a plane. And a step of heating and foaming the foamable thermoplastic resin sheet, in which the foamable thermoplastic resin granules are integrally connected via a foamable thermoplastic resin thin film, at or above the decomposition temperature of the foaming agent. Forming a concave and convex by cooling in a cooling mold having voids over which the foam obtained by foaming is completely filled, so that the compressive strength,
The thermoplastic resin foam according to claims 1 to 7 having excellent quality such as cushioning property and thickness accuracy and having little variation in quality can be manufactured with high productivity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a thermoplastic resin foam according to the first or third aspect of the present invention.

FIG. 2 is a virtual projection view in which the thermoplastic resin foam of FIG. 1 is projected on a projection plane orthogonal to a thickness direction.

FIG. 3 is a sectional view showing an example of the thermoplastic resin foam according to the invention of claim 7;

FIG. 4 is a virtual projection view in which the thermoplastic resin foam of FIG. 3 is projected on a projection plane orthogonal to the thickness direction.

FIG. 5 is a virtual projection view of projecting the thermoplastic resin foam according to the invention of claim 7 onto a projection plane orthogonal to the thickness direction.

FIG. 6 is a cross-sectional view showing an example of the thermoplastic resin foam according to the invention of claim 7 cited in claim 2;

FIG. 7 is a cross-sectional view illustrating a foaming step of a method for producing the thermoplastic resin foam of the invention according to the seventh aspect of the present invention by citing the second aspect.

FIG. 8 is a cross-sectional view for explaining a cooling step in a method of manufacturing by the manufacturing method according to claim 8;

FIG. 9 is a schematic side view for explaining a step of producing a foamable thermoplastic resin sheet used in the production method according to claim 8;

[Explanation of symbols]

 1, 11, 31 Thermoplastic resin foam 2, 12, 32 Continuous foam layer 3, 13, 33 High foam part 4, 14, 34 Low foam thin film 5, 15, 35 Continuous surface 6, 16, 36 Discontinuous surface 25 Expandable thermoplastic resin granules 26 Expandable thermoplastic resin thin film 27 Expandable thermoplastic resin sheet 30 Cooling type

Claims (8)

[Claims] 1. A continuous foamed layer made of a thermoplastic resin, a highly foamed portion made of a thermoplastic resin disposed on at least one surface of the continuous foamed layer, and an outer surface of the highly foamed portion together with the continuous foamed layer. A plate-like body made of a thermoplastic resin foam provided with a low-foaming thin film made of a thermoplastic resin to be coated, and when the foam is projected on a projection surface orthogonal to the thickness direction, only the continuous foam layer, Or a continuous surface on which only the continuous foam layer and the low-foaming thin film are projected, and a discontinuous surface on which the continuous foaming layer, the low-foaming thin film and the high-foaming portion are projected, and a portion of the foam corresponding to the discontinuous surface However, a thermoplastic resin foam characterized in that at least one surface is formed in a convex shape with respect to a portion of the foam corresponding to the continuous surface. 2. A continuous foamed layer made of a thermoplastic resin, a high foamed portion made of a thermoplastic resin disposed on at least one surface of the continuous foamed layer, and an outer surface of the high foamed portion together with the continuous foamed layer. A plate-like body made of a thermoplastic resin foam provided with a low-foaming thin film made of a thermoplastic resin to be coated, and when the foam is projected on a projection surface orthogonal to the thickness direction, only the continuous foam layer, Or a continuous surface on which only the continuous foam layer and the low-foaming thin film are projected, and a discontinuous surface on which the continuous foaming layer, the low-foaming thin film and the high-foaming portion are projected, and a portion of the foam corresponding to the discontinuous surface However, a thermoplastic resin foam characterized in that at least one surface is formed in a convex shape and the other surface is formed in a concave shape with respect to a portion of the foam corresponding to the continuous surface. 3. The thermoplastic resin foam according to claim 1, wherein the highly foamed portions are arranged in a lattice. 4. The thermoplastic resin foam according to claim 1, wherein the highly foamed portions are arranged in a staggered manner. 5. The high-foamed portion, the outer surface of which is covered with the low-foaming thin film, has a convex portion having a height of 1 mm or more with respect to a continuous surface. 4. The thermoplastic resin foam according to claim 1. 6. The volume of the thermoplastic resin foam is 5 to the minimum volume of the rectangular parallelepiped that can circumscribe the thermoplastic resin foam.
The thermoplastic resin foam according to any one of claims 1 to 5, wherein the content is 0 to 90%. 7. The method according to claim 1, wherein the plurality of high foaming portions are heat-sealed to each other via a low foaming thin film.
7. The thermoplastic resin foam according to 6. 8. A foamable thermoplastic resin granule containing a foaming agent is substantially uniformly arranged in a plane, and the foamable thermoplastic resin granule is interposed via a foamable thermoplastic resin thin film. A step of heating the foamed thermoplastic resin sheet integrally connected to the foaming agent at a temperature higher than the decomposition temperature of the foaming agent and foaming the foamed foam; Forming irregularities by cooling in a mold. A method for producing a thermoplastic resin foam, comprising: