JP3279498B2 - Composite thermoplastic resin foam sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed thermoplastic resin sheet, and more particularly, to a foamed thermoplastic resin sheet obtained by foaming a thermoplastic resin sheet containing a pyrolytic foaming agent. The present invention relates to a composite thermoplastic resin foam sheet obtained by laminating materials.

[0002]

2. Description of the Related Art Thermoplastic foams are widely used for various heat insulating materials such as roof heat insulating materials and floor heat insulating materials, cushioning materials or floating materials because of their excellent lightness, heat insulating properties and flexibility. ing.

However, the conventional foamed thermoplastic resin sheet has a problem that the strength, for example, the compressive strength is not sufficient. For example, as disclosed in Japanese Patent Publication No. 48-9955, in an ethylene-based resin foam sheet, cells produced by foaming have a spindle shape due to the characteristics of the production method, and the major axis of the cell is in the longitudinal direction of the foam. The cells are formed such that the short axis is oriented in the thickness direction of the foam. Therefore, when the foam receives a compressive force in the thickness direction,
Since the compressive force acts in the short axis direction of the cell, there is a problem that the compressive strength is reduced.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite foamed thermoplastic resin sheet which has improved compressive strength by eliminating the drawbacks of conventional thermoplastic resin foam sheets.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a composite heat source.
The plastic resin foam sheet is made of a thermoplastic resin containing a pyrolytic foaming agent.
Composite foaming in which a sheet-like material is laminated and integrated on a fat sheet
Composite thermoplastic resin obtained by heating and foaming the sheet
A foam sheet, comprising two or more incompatible thermoplastic trees
Fat blended, and any one of the thermoplastic resins
From thermoplastic resin with only cross-linking and pyrolytic foaming agent
Comprising at least one surface of the thermoplastic resin foam sheet obtained from the thermally decomposable foaming agent-containing thermoplastic resin sheet, foaming power in the in-plane direction generated when the heating and foaming the thermally decomposable foaming agent-containing thermoplastic resin sheet It is characterized in that the sheet-like material in which the above is suppressed is laminated and integrated.

A feature of the present invention is an in-plane direction generated when a thermoplastic resin foam sheet is heated and foamed from a thermoplastic resin sheet containing a pyrolytic foaming agent (hereinafter sometimes abbreviated as a thermoplastic resin sheet). Since the sheet-like material having suppressed foaming force is laminated on at least one surface of the thermoplastic resin foam sheet, foaming in the in-plane direction is suppressed, and cells formed by the suppressed amount are formed in the thickness direction. In other words, the shape has a long axis, thereby increasing the compressive strength. In addition, since the sheet-like material is laminated and integrated, the strength of the entire composite thermoplastic resin foam sheet is also increased by the reinforcing effect of the sheet-like material itself.

[0007] In the composite thermoplastic resin foam sheet according to the present invention, preferably, the foam cell formed in the thermoplastic foam sheet has a major axis oriented substantially in the thickness direction.

In the present invention, the in-plane direction refers to a two-dimensional direction defined by the longitudinal direction and the width direction of the composite thermoplastic resin foam sheet, and refers to a direction orthogonal to the thickness direction. .

[0009] More preferably, the ratio of the major axis to the minor axis of the foam cell is 2 or more, whereby the compressive strength is further enhanced. More preferably, the density at the center in the thickness direction is smaller than the density at the surface.

Hereinafter, the present invention will be described in detail. In the present invention, the sheet-like material is provided to suppress in-plane foaming. Therefore, if the strength of the sheet-like material is too low, the sheet-like material is torn at the time of foaming, and the foaming in the in-plane direction of the blowing agent-containing thermoplastic resin sheet cannot be sufficiently suppressed, and the strength is too high. Then, the flexibility of the obtained composite thermoplastic resin foam sheet decreases.

Therefore, as the sheet-like material, one having a tensile strength capable of suppressing the foaming is used. For example, when the foaming ratio is 5 times or less, the tensile strength is 0.4%.
When the expansion ratio is 5 to 10 times, the tensile strength is 0.8 to 10 kgf / cm, and when the expansion ratio is 10 times or more, the tensile strength is 10 to 100 kgf.
/ Cm range is used.

The material constituting the sheet-like material is not particularly limited. To laminate and integrate with the foaming agent-containing thermoplastic resin sheet, a certain degree of adhesion between the foaming agent-containing thermoplastic resin sheet and the foaming agent-containing thermoplastic resin sheet is required. Desirable ones include, for example, surface mats usually obtained by forming short glass fibers, glass cloth formed by weaving glass fibers, paper, woven fabrics and nonwoven fabrics made of organic or inorganic fibers, and the like. Can be.

[0013] The surface mat may contain a binder for binding the short glass fibers to each other. The binder is not particularly limited as long as the tensile strength of the sheet material satisfies the above range, and for example, a binder made of a thermoplastic resin or a thermosetting resin can be used. Examples of the thermoplastic resin that can be used as the binder include polyvinyl alcohol, saturated polyester, and acrylic resin. Examples of the thermosetting resin include epoxy resin and unsaturated polyester.

The organic fibers constituting the woven or nonwoven fabric include polyester fibers, cotton, acrylic fibers, nylon fibers, carbon fibers, and aramid fibers.

Regarding the method of laminating and integrating the sheet-like material on the foaming agent-containing thermoplastic resin sheet, as long as the foaming agent-containing thermoplastic resin sheet and the sheet-like material are fixed,
There is no particular limitation. For example, a method in which a foaming agent-containing thermoplastic resin sheet is heated to a molten state and thermally fused to a sheet-like material, a method in which a foaming agent-containing thermoplastic resin sheet and a sheet-like material are bonded with an adhesive, and the like are exemplified. can do.

More specifically, a sheet-like material is lightly laminated on both the upper and lower surfaces of a foaming agent-containing thermoplastic resin sheet extruded from a T-die, and is passed between a pair of opposed cooling rolls to press the roll. A preferred method is to integrate the two.

The lamination / integration means that a high ratio (usually 50%) is obtained when the thermoplastic resin sheet containing the foaming agent and the sheet material are to be separated at the interface between them.
(Preferably 70% or more) in a state where both are fixed to such an extent that the material is destroyed.

In the present invention, the thermoplastic resin constituting the foaming agent-containing thermoplastic resin sheet is not particularly limited, and examples thereof include low-density polyethylene, high-density polyethylene, and linear low-density polyethylene (hereinafter, referred to as “low-density polyethylene”). , Polyethylene is meant to include these or mixtures thereof), olefin resins such as polypropylene (hereinafter, polypropylene includes homopolypropylene, block polypropylene, and random polypropylene); Vinyl, chlorinated polyvinyl chloride, ABS resin, polystyrene, polycarbonate, polyamide, polyvinylidene fluoride, polyphenylene sulfide, polysulfone, polyetheretherketone, and copolymers thereof can be used. Further, these resins may be used alone or in combination of two or more.

If the melt index (MI) of the thermoplastic resin is too large or too small, the foaming stability is reduced. Therefore, the MI of the thermoplastic resin is 0.1 to 2
0 g / 10 min.
More preferably, the range is 10 g / 10 minutes. In addition, MI in this specification is a value measured according to JIS K7210.

The above thermoplastic resin is preferably crosslinked from the viewpoint of foaming stability. 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, or a silane crosslinking method using a silane-modified resin. And the like.

If the degree of cross-linking is too high, the expansion ratio decreases, and the thermoformability also decreases. If the degree of cross-linking is too low, the thermal stability decreases and the cells break at the time of foaming, so that uniform cells can be obtained. May disappear. Therefore, the gel fraction serving as an indicator of crosslinking is preferably in the range of 10 to 30% by weight,
5% by weight is more preferred.

The above gel fraction is defined as the cross-linking resin of the foaming agent-containing thermoplastic resin sheet before immersion in xylene before immersion in the xylene at 120 ° C. for 24 hours. The weight percentage is based on the partial weight.

In the present invention, as the thermoplastic resin constituting the foaming agent-containing thermoplastic resin sheet, an incompatible 2
By blending more than one type of thermoplastic resin and crosslinking only one of the thermoplastic resins, the fluidity of the resin during foaming can be secured by the high fluidity of the non-crosslinked portion.

By doing so, the foaming pressure during foaming is reduced as compared with a foaming agent-containing thermoplastic resin sheet uniformly cross-linked using a single thermoplastic resin, and the foaming agent-containing thermoplastic resin is used. It is possible to make the sheet-like material laminated on the surface of the sheet more difficult to break. This makes it easier to suppress in-plane foaming of the foaming agent-containing thermoplastic resin sheet and to allow the suppressed portion to be foamed in the thickness direction.

When two or more kinds of thermoplastic resins are used as described above, the phase-separated sea-island structure can be controlled by changing the melt viscosity ratio of the two or more kinds of thermoplastic resins. It is. For example, when the melt viscosity ratio is increased, it is possible to develop a uniform and fine sea-island structure.

In the present invention, in order to ensure the flowability of the foaming agent-containing thermoplastic resin sheet during foaming, it is preferable that the thermoplastic resin sheet has a uniform and fine sea-island structure to some extent. When it is set to about 4 to 10, it becomes possible to develop a targeted uniform fine morphology. In this case, the particle size of the island portion in the sea-island structure is about 1 to 100 μm.

The mixing ratio of two or more thermoplastic resins is such that the resulting non-crosslinked portion of the thermoplastic resin sheet containing the foaming agent has a non-crosslinked portion of 30% in order to secure necessary fluidity during foaming.
Preferably, the ratio is such that the ratio occupies ~ 70%. Only one of the two or more thermoplastic resins is crosslinked.

Among the thermoplastic resins mixed with two or more kinds,
As means for preferentially crosslinking only one type, for example, a method of mixing a crosslinking aid such as divinylbenzene in the case of the electron beam crosslinking method, and a method of mixing two or more kinds of thermoplastic resins in the case of the silane crosslinking method. Among them, a silane-modified thermoplastic resin of the same kind as the thermoplastic resin to be cross-linked and a cross-linking catalyst are added, followed by water treatment.

The above-mentioned water treatment means that a blowing agent-containing thermoplastic resin sheet to which a silane-modified thermoplastic resin is added is hydrolyzed by dipping it in water to cause a crosslinking reaction. In order to promote cross-linking, it is preferable to use hot water as the water, and specifically, it is achieved by immersing in hot water at 100 ° C. for 2 hours or more.

Specific examples of the crosslinking catalyst include dibutyltin dilaurate, octanetin barium and the like.
If the addition amount of the silane crosslinking catalyst is large, the expansion ratio of the obtained foamed sheet is reduced, and if the addition amount is small, the crosslinking reaction rate is reduced and time is required for water treatment.
0.001 to 10 parts by weight, preferably 0.01 to 0.1 parts by weight, based on 0 parts by weight.

A method for crosslinking a thermoplastic resin with the above peroxide will be described. The peroxide used in the present invention is not particularly limited, and examples thereof include dibutyl peroxide, dicumyl peroxide, tert-butyl cumyl peroxide, diisopropyl peroxide and the like, and dicumyl peroxide, tert-butyl cumyl peroxide. Oxides are preferred, and dicumyl peroxide is particularly preferred.

If the amount of the peroxide is large, the decomposition reaction of the resin proceeds, and the resulting foam may be colored. If the amount is small, the crosslinking of the thermoplastic resin may be insufficient. Therefore, with respect to 100 parts by weight of the thermoplastic resin, 0.
Preferably 5 to 5 parts by weight, more preferably 1 to 3 parts by weight.

The method of irradiating the above-mentioned radiation to crosslink the thermoplastic resin will be described. When the irradiation amount of radiation is large, crosslinking is excessively applied, and the expansion ratio of the obtained foam is reduced,
On the other hand, if the amount is small, the thermal stability is reduced, the cells are broken, and it is difficult to obtain a uniform cell. Therefore, 1 to 20 Mrad is preferable, and 3 to 10 Mrad is particularly preferable.

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

The pyrolyzable foaming agent contained in the foaming agent-containing thermoplastic resin sheet used in the present invention is generally used in the production of foams, and is prepared by melting the foaming agent-containing thermoplastic resin sheet. Any blowing agent having a decomposition temperature above the temperature can be used.

Examples of usable blowing agents include inorganic pyrolytic blowing agents such as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, azide compounds, sodium borohydride, azodicarbonamide, azobisisobutyronitrile. , N, N'-dinitrosopentamethylenetetramine, P, P'-dinitrosopentamethylenetetramine,
p, p'-oxybisbenzenesulfonyl hydrazide,
Examples include barium azodicarboxylate, trihydrazinotriazine, p-toluenesulfonyl semicarbazide, and the like.Especially, since the decomposition peak temperature and the decomposition rate are easily adjusted, the amount of generated gas is large, and hygiene is excellent, It is preferred to use amides.

The amount of the thermal decomposition type foaming agent to be added is determined according to the target expansion ratio. For example, if azodicarbonamide is used, 239 cm ² of gas is generated per gram. Therefore, when 1 part of azodicarbonamide is added per 100 g of the thermoplastic resin, a foam having an expansion ratio of 2.39 times is usually obtained. Can be

In order to obtain the above-mentioned foaming agent-containing thermoplastic resin sheet, a resin composition containing the above-mentioned thermoplastic resin and a pyrolytic foaming agent may be melt-kneaded into a sheet by a general method. The method is not particularly limited.
However, it is preferable to use a twin-screw kneading extruder since the kneading degree can be increased and the foaming stability can be increased. However, the method of forming the melt-kneaded resin composition into a sheet is not limited to extrusion using an extruder.

When the above-mentioned electron beam crosslinking or silane crosslinking is carried out, a step of forming the above resin composition into a sheet shape and, after this step, a treatment according to a crosslinking method may be carried out. In this case, a cross-linking treatment may be performed at the stage of the foaming agent-containing thermoplastic resin sheet, or a stage after laminating and integrating a sheet-like material for suppressing foaming described above on the foaming agent-containing thermoplastic resin sheet. May be performed.

Next, the above-mentioned foaming agent-containing thermoplastic resin sheet is laminated with a sheet-like material for suppressing the above-mentioned foaming force and integrated to obtain a composite foamable sheet. This step can be performed by an appropriate method described above.

Next, the obtained composite foamable sheet is foamed by heating to a temperature equal to or higher than the decomposition temperature of the pyrolytic foaming agent. Thereafter, the thermoplastic resin is cooled to a temperature equal to or lower than the softening temperature of the thermoplastic resin, and the sheet is solidified to obtain the composite thermoplastic resin foam sheet of the present invention. In this case, the method of heating and cooling is not particularly limited.

For example, as a heating method, a composite foaming sheet is put into a heating furnace whose inside is maintained at a constant temperature, hot air is blown on the composite foaming sheet, or two heating rollers facing each other are heated. The separation can be performed by passing through a composite foamable sheet while being in contact with a heating roller.

As a cooling method, a method of blowing cold air, a method of adjusting the temperature of the resin up and down to a temperature lower than the melting temperature of the resin with cold water.
A method of passing the composite foamable sheet between two belts, a method of passing the composite foamable sheet between two opposed cooling rollers, and the like can be given.

When the foaming agent-containing thermoplastic resin sheet in the composite foamable sheet is foamed by heating, it may be foamed freely, but it is desirable to foam by heating between the upper and lower two belts. That is, by arranging and foaming the composite foamable sheet between the upper and lower two belts, the adhesiveness of the sheet-like material for suppressing foaming to the foamed sheet side can be increased, and the in-plane direction can be improved. Foaming can be suppressed more effectively, whereby the expansion force in the in-plane direction of the sheet during foaming can be reliably suppressed.

The belt may be made of a material which can adhere when the thermoplastic resin constituting the foaming agent-containing thermoplastic resin sheet melts, but which does not adhere to the thermoplastic resin sheet by cooling. It is desirable to use. Therefore, the belt is preferably made of a material having a higher melting temperature than the thermoplastic resin.Specifically, from the viewpoint of releasability after foaming, it is more preferable to use a belt mainly composed of polytetraethylene. Preferably, more preferably, a cloth obtained by impregnating and coating tetrafluoroethylene on a cloth woven of inorganic fibers, firing at a high temperature, and performing belt processing can be mentioned. Specifically, Chuko Kasei Kogyo Co., Ltd.
Product name: Chuko Flow G type belt can be exemplified.

In the present invention, preferably, the cells formed by foaming have their major axes oriented substantially in the thickness direction of the foamed thermoplastic resin sheet. That is, since at least one surface of the thermoplastic resin foam sheet is laminated with a sheet-like material that suppresses in-plane foaming during foaming, all foaming forces act in the thickness direction of the composite thermoplastic resin foam sheet during the foaming process. Will be.

As a result, since the cells in the obtained composite thermoplastic resin foam sheet extend only in the thickness direction of the foam sheet, the major axis is substantially oriented in the thickness direction of the composite thermoplastic resin foam sheet. .

In the present invention, the above-mentioned foaming agent-containing thermoplastic resin sheet is laminated and integrated with the above-mentioned sheet-like material having suppressed foaming power. As a result, the foaming ratio in the thickness direction is 60% or more. And preferably 80% or more.

In the present invention, more preferably, the ratio of the major axis to the minor axis of the cell is 2 or more, whereby
The compressive strength in the thickness direction is further increased. The ratio between the major axis and the minor axis can be controlled by the expansion ratio and the melt viscosity of the thermoplastic resin containing a foaming agent. Increasing the expansion ratio increases the expansion ratio in the thickness direction, thereby increasing the ratio of the major axis to the minor axis of the cell. In particular,
Melting viscosity of foaming agent-containing thermoplastic resin is from 8000 poise
In the region of 25,000 poise, the expansion ratio is 5 or more and less than 10 times, the ratio of the major axis to the minor axis is 2 or more, and the
The ratio of the major axis to the minor axis becomes 2.5 or more at twice or more.

The melt viscosity in the present specification is J
This is a value measured according to IS K7199. When the melt viscosity of the resin is less than 8000 poise, the melt viscosity of the resin is insufficient, and when the foaming agent-containing thermoplastic resin expands in the thickness direction at the time of foaming, the resin film of the cell is broken, and the cell becomes a spindle shape. Hard to be. If it exceeds 25,000 poise, the cell does not expand in the thickness direction at the time of foaming, so that the cell becomes substantially spindle-shaped. In this case, the ratio of the major axis to the minor axis does not become 2 or more.

In the present invention, more preferably, in the composite thermoplastic resin foam sheet, the density at the center in the thickness direction is made smaller than the density of the surface layer. Since at least one surface of the composite thermoplastic resin foam sheet is laminated with a sheet-like material that suppresses in-plane foaming at the time of foaming, cells near the surface cause foam breakage to some extent during the foaming process. As a result, the surface portion has a higher density than the central layer of the composite thermoplastic resin foam sheet.

In order to achieve the object of the present invention, it is necessary that the blowing agent-containing thermoplastic resin has a certain degree of fluidity at the time of foaming. As described above, it is desirable to blend two or more incompatible thermoplastic resins as described above and to crosslink one of the resins.

In the composite thermoplastic resin foam sheet according to the first aspect of the present invention, the sheet material is laminated and integrated on at least one surface of the thermoplastic resin foam sheet. When obtained by foaming from the pyrolytic foaming agent-containing thermoplastic resin sheet, since the sheet-like material suppresses the in-plane foaming force, foaming in the thermoplastic resin foam sheet in the composite thermoplastic resin foam sheet is suppressed. It is preferentially guided in the thickness direction. At that time, the thermal decomposition type foaming agent containing heat
Two or more types of incompatible heat that constitute the plastic resin sheet
Only one of the thermoplastic resins is crosslinked
The high flowability of the non-crosslinked part
To ensure the fluidity of the resin during foaming.
Foam pressure is reduced and uniform using a single thermoplastic resin
Compared to crosslinked thermoplastic resin sheet containing pyrolytic foaming agent
Be, laminated sheet on the surface of thermoplastic resin foam sheet
It is possible to make the object more difficult to break. this
Thereby, the sheet-like material suppressed in-plane foaming,
It becomes easy to foam the part only in the thickness direction. Therefore, since the cells formed by foaming in the composite thermoplastic resin foam sheet are foamed such that the major axis is in the thickness direction, the compressive strength in the thickness direction of the composite thermoplastic resin foam sheet is increased. Will be.

According to the second aspect of the present invention, since the cells formed by foaming are configured so that their major axes are oriented substantially in the thickness direction, the compressive strength in the thickness direction is further enhanced.

According to the third aspect of the present invention, the cell is configured so that the ratio of the major axis to the minor axis is 2 or more.
Similarly, the compressive strength in the thickness direction is further increased. According to the fourth aspect of the present invention, since the density at the central portion in the thickness direction is lower than the density at the surface portion, the surface becomes relatively hard, so that the strength against external force in the thickness direction can be increased.

[0056]

EXAMPLES The present invention will be described in more detail with reference to examples of the present invention, but the present invention is not limited to these examples.

(Raw Materials) The following thermoplastic resin, silane-modified thermoplastic resin, silane crosslinking catalyst, and pyrolytic foaming agent were prepared.

Thermoplastic resin HDPE1: high-density polyethylene, manufactured by Mitsubishi Chemical Corporation, trade name: BX50A, density = 0.958 g / cm ³ , MI
= 0.35 / 10 minutes. HDPE2: High-density polyethylene, manufactured by Mitsubishi Chemical Corporation, trade name: HY340, density = 0.952 g / cm ³ , MI
= 1.5 g / 10 min. HDPE3: high-density polyethylene, manufactured by Mitsubishi Chemical Corporation, trade name: JY20, density = 0.951 g / cm ³ , MI =
9.0 / 10 minutes. PP1: polypropylene, manufactured by Mitsubishi Chemical Corporation, trade name: M
H8, density = 0.900 g / cm ³ , MI = 0.30 g
/ 10 minutes. PP2: polypropylene, manufactured by Mitsubishi Chemical Corporation, trade name: M
A3, density = 0.900 g / cm ³ , MI = 11 g / 1
0 minutes.

Silane-modified thermoplastic resin Silane-modified PE: Silane-modified polyethylene, manufactured by Mitsubishi Chemical Corporation, trade name: HM600A, density = 0.963 g / c
m ³ , MI = 10 g / 10 min. Silane-modified PP: Silane-modified polypropylene, manufactured by Mitsubishi Chemical Corporation, trade name: XPM800HM, density = 0.91
2 g / cm ³ , MI = 11 g / 10 min.

Silane cross-linking catalyst Silane cross-linking catalyst 1: Master batch of dibutyltin dilaurate / high-density polyethylene = 1/100: manufactured by Mitsubishi Chemical Corporation. Silane cross-linking catalyst 2: dibutyltin dilaurate / polypropylene = 1/100 master batch ... Mitsubishi Chemical Corporation, trade name: PZ-10S.

Thermal decomposition type blowing agent azodicarbonamide manufactured by Otsuka Chemical Co., Ltd., trade name: SO-
20, decomposition temperature = 201 ° C.

Example 1 The above thermoplastic resin, silane-modified thermoplastic resin, silane crosslinking catalyst, and pyrolytic foaming agent were mixed in the proportions (parts by weight) shown in Table 1 below, and mixed with a twin-screw extruder. It was melt-kneaded. Further, as shown in FIG.
It was extruded into a sheet shape from a T-die 1 having a lip opening of 1.1 mm and a lip opening of 10 mm to obtain a pyrolytic foaming agent-containing thermoplastic resin sheet 2 having a width of 450 mm and a thickness of 1.0 mm. Furthermore, T
Non-woven fabrics 3 and 4 of polyethylene terephthalate (weighing 30 g / m ² , tensile strength: 1.6 kgf / cm in height, horizontal: 1.) above and below a thermoplastic resin sheet 2 containing a pyrolytic foaming agent extruded from a die 1. (2 kgf / cm, manufactured by Toyobo Co., Ltd.), and then passed between opposed cooling rolls 5 and 6 each having an interval of 0.9 mm and a temperature set at 25 ° C., and laminated and integrated to form a composite foaming material. Sheet 7 was obtained.

The composite foamable sheet 7 obtained as described above
Was cut into a size of 400 mm in width × 1000 mm in length to obtain a composite foamable sheet 7 shown in FIG. In this composite foamable sheet 7, nonwoven fabrics 3 and 4 as the above-mentioned sheet-like material are laminated above and below the foaming agent-containing thermoplastic resin sheet 2.

Next, the composite foamable sheet 7 was immersed in hot water of 99 ° C. for 2 hours to be crosslinked. Further, the composite foamable sheet is sandwiched between two upper and lower two belts mainly composed of polytetrafluoroethylene (manufactured by Chuko Kasei Kogyo Co., Ltd., trade name: Chuko Flow G type belt) and heated to a temperature of 230 ° C. And foamed. After foaming, the mixture was cooled to solidify the thermoplastic resin sheet containing the pyrolytic foaming agent, and the composite foamable sheet was separated from the belt to obtain a composite thermoplastic resin foam sheet.

Further, the gel fraction of the resin portion not containing the sheet-like material of the above-mentioned composite thermoplastic resin foam sheet was measured under the above-mentioned conditions (120 ° C., 24 hours, hot xylene extraction). The results are shown in Table 2 below.

As shown in FIG. 3, in the composite thermoplastic resin foam sheet 8 obtained, the foaming in the in-plane direction was hardly caused by the nonwoven fabrics 3 and 4 because the non-woven fabrics 3 and 4 suppressed the foaming. It was recognized that only the foam was large.

In order to confirm the above observation results, (1) thickness accuracy of the obtained composite thermoplastic resin foam sheet,
(2) The area increase rate due to in-plane foaming, (3) the overall foaming ratio of the composite thermoplastic resin foam sheet, (4) the thickness direction foaming ratio, and (5) the thickness direction foaming ratio, are non-woven fabrics as sheet-like materials. Are shown in Table 2 below together with the tensile strength. The evaluation criteria and the measurement of the tensile strength were performed in the following manner. In addition, the melt viscosity of the resin portion of the foaming agent-containing thermoplastic resin sheet before foaming was measured. The melt viscosity is shown in Table 1 below.

(1) Sheet tensile strength: JIS P
A tensile test was performed in accordance with 8113, and a load in which the load-elongation relationship deviated from a linear relationship was defined as a maximum load, and the maximum load was divided by the sample width at that time to determine a tensile strength. (2) Thickness accuracy: Measure the maximum thickness and the minimum thickness, and calculate (maximum thickness-target thickness) / (target thickness) and (minimum thickness-target thickness) / (target thickness). The thickness accuracy in the + direction and the-direction was evaluated based on the calculated values.

(3) Area increase rate: It was determined by {(plane area of foamed composite thermoplastic resin sheet / plane area of foamed composite foam sheet before foaming) -1} × 100 (%). (4) Thickness expansion ratio: calculated by (thickness of foamed composite thermoplastic resin sheet / thickness of foamed composite sheet). (5) Foaming ratio in thickness direction: (Thickness of foamed composite thermoplastic resin sheet-thickness of foamed composite sheet) / (thickness of foamed composite sheet) × 100 (%).

Further, the obtained composite thermoplastic resin foam sheet was cut in the thickness direction, and the cut cross section was observed with an optical microscope. As a result, a spindle-shaped foam cell was formed. The length of the major axis and the minor axis of the foam cell were measured using a reference scale, and the ratio of the major axis to the minor axis was determined. The results are shown in Table 3 below.

Further, the composite thermoplastic resin foam sheet obtained as described above is cut at a two-dimensional cross section with the normal in the thickness direction, and the vicinity of the surface layer and the thickness direction of the composite thermoplastic resin foam sheet are measured. The central part was taken out and the density at each part was determined. Here, in the density measurement part,
The sheet-like material laminated on the surface of the composite thermoplastic resin foam sheet was not included. The determined surface layer density and internal layer density are shown in Table 3 below.

Further, the obtained composite thermoplastic resin foam sheet was cut so as to have a planar shape of 5 cm × 5 cm, and the 25% compressive strength when pressure was applied in the thickness direction was measured according to JIS.
It was measured according to K6767. The results are shown in Table 3 below.

The flexural strength of the composite foamed thermoplastic resin sheet obtained as described above was evaluated in the following manner. Measurement of flexural strength: A sample having a length of 200 mm × a width of 25 mm and a thickness of 10 mm was taken out of the obtained composite thermoplastic resin foam sheet, and the flexural strength in the flow direction and the width direction was measured according to JIS K7221. The results are shown in Table 3 below.

Examples 2 to 8 The same procedures as in Example 1 were carried out except that the thermoplastic resin, the silane-modified thermoplastic resin and the silane crosslinking catalyst used were changed as shown in Table 1 below. A composite-type thermoplastic resin foam sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Tables 1 to 3 below.
Shown in

(Comparative Example 1) A sheet material laminated on and under a foaming agent-containing thermoplastic resin sheet extruded from a T die was woven with a non-woven fabric (weighing 10 g / m ² , tensile strength: 0.
36 kg / cm, width 0.18 kg / cm, manufactured by Toyobo Co., Ltd., trade name: Spunbond Equle 6101A), except that a composite thermoplastic resin foam sheet was produced in the same manner as in Example 1, Evaluation was performed in the same manner as in Example 1. The results are shown in Tables 1 to 3 below.

(Comparative Example 2) A sheet material laminated on and under a foaming agent-containing thermoplastic resin sheet extruded from a T-die was woven with a nonwoven fabric (weighing 20 g / m ² , tensile strength: 0.
92 kg / cm, width 0.60 kg / cm, manufactured by Toyobo Co., Ltd., trade name: Spunbond Equle 6201A), except that the composite thermoplastic resin foam sheet was produced in the same manner as in Example 1, Evaluation was performed in the same manner as in Example 1. The results are shown in Tables 1 to 3 below.

(Comparative Example 3) A foaming agent-containing thermoplastic resin sheet was produced without laminating a nonwoven fabric on the surface of the foaming agent-containing thermoplastic resin sheet used in Example 1, and was heated at 230 ° C in the same manner as in Example 1. To obtain a foamed thermoplastic resin sheet.

Thereafter, the thermoplastic resin foam sheet is heated to 200 ° C. to re-melt the surface, and a polyethylene terephthalate non-woven fabric (manufactured by Toyobo Co., Ltd., trade name: Spunbond Ecule 6301A) is laminated by heat fusion. ,
A composite thermoplastic resin foam sheet was obtained. About the composite thermoplastic resin foam sheet thus obtained, Example 1
Was evaluated in the same way as The results are shown in Tables 1 to 3 below.

[0079]

[Table 1]

[0080]

[Table 2]

[0081]

[Table 3]

[0082]

In the composite thermoplastic resin foam sheet according to the present invention, a sheet material is laminated and integrated on at least one surface of the thermoplastic resin foam sheet and reinforced, and the sheet material is formed of a thermoplastic resin. When the foamed sheet is obtained by foaming from a thermoplastic resin sheet containing a pyrolytic foaming agent, the foaming force in the in-plane direction is suppressed. Therefore, in the composite thermoplastic resin foam sheet according to the first aspect, since foaming is preferentially guided in the thickness direction, the compressive strength in the thickness direction is increased. At this time, the thermal decomposition type foaming agent containing heat
Two or more types of incompatible heat that constitute the plastic resin sheet
Only one of the thermoplastic resins is crosslinked
Has been used to achieve uniformity using a single thermoplastic resin.
Thermoplastic resin sheet containing pyrolytic foaming agent cross-linked
Foaming pressure during foaming is lower than that of
For further breaking the sheet material laminated on the foam sheet surface
It is possible to make it. This allows foaming
In-plane foaming is reliably suppressed, and the suppressed amount
To be able to be foamed in the thickness direction
It can be easier, and the compressive strength in the thickness direction is further increased
Can be

In the foamed composite thermoplastic resin sheet according to the second aspect of the present invention, since the long axis of the foamed cells is oriented substantially in the thickness direction, the compressive strength in the thickness direction can be further increased.

In the composite thermoplastic resin foam sheet according to the third aspect of the present invention, since the ratio of the major axis to the minor axis of the foam cell is 2 or more, the compressive strength in the thickness direction can be further increased. In the composite thermoplastic resin foam sheet according to the fourth aspect of the present invention, since the density at the center in the thickness direction is smaller than the density at the surface portion, the compressive strength in the thickness direction can be further increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a process of laminating and integrating paper as a sheet material on a thermoplastic resin sheet containing a pyrolytic foaming agent in Example 1.

FIG. 2 is a perspective view showing a composite foamable sheet formed by laminating paper as a sheet material on a pyrolytic foaming agent-containing thermoplastic resin sheet.

FIG. 3 is a perspective view for explaining a composite thermoplastic resin foam sheet obtained by heating and foaming the composite foamable sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... T die of an extruder 2 ... Thermoplastic resin sheet containing a pyrolysis type foaming agent 3, 4 ... Paper as a sheet material 5, 6 ... Cooling roll 7 ... Composite foamable sheet 8 ... Composite thermoplastic resin foam sheet

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-70621 (JP, A) JP-A-1-185338 (JP, A) JP-A-10-45934 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B32B 5/18 C08J 9/06

Claims (4)

(57) [Claims] 1. A thermoplastic resin sheet containing a pyrolytic foaming agent.
Composite foamed sheet in which sheet materials are laminated and integrated
Composite thermoplastic resin foam sheet obtained by heating and foaming
And incompatible two or more thermoplastic resins
And mount only one of the thermoplastic resins.
On at least one side of a thermoplastic resin foam sheet obtained from a bridged thermoplastic resin and a pyrolytic foaming agent-containing thermoplastic resin sheet composed of a pyrolytic foaming agent, the pyrolytic foaming agent-containing thermoplastic resin sheet A composite thermoplastic resin foam sheet characterized in that a sheet-like material having suppressed in-plane foaming force generated upon heating and foaming is laminated and integrated. 2. The composite thermoplastic resin foam sheet according to claim 1, wherein a long axis of the foam cells formed in the thermoplastic resin foam sheet is oriented substantially in a thickness direction. 3. The composite thermoplastic resin foam sheet according to claim 2, wherein the ratio between the major axis and the minor axis of the foam cell is 2 or more. 4. The composite thermoplastic resin foam sheet according to claim 2, wherein the density at the center in the thickness direction is lower than the density at the surface.