JPH07106591B2 - Styrene resin foam - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a styrene resin foam produced by extrusion foaming, and in particular, a high quality styrene resin foam having a large compressive strength in a bent state. It is about the body.

(Prior Art) Styrenic resin foams are used in various fields. For example, thin sheets are used after being processed into containers and the like, and thick plates are used as tatami floors, floors and wall materials for frozen warehouses, and the like.

It is known that an extrusion foaming method is suitable for producing a styrene resin foam. The extrusion foaming method is a method in which a resin is melted in an extruder, a foaming agent is pressed into the extruder, and the resin is foamed at the same time as the resin is extruded from the extruder to obtain a foamed body having a uniform cross section. Is.

Various foaming agents were used. The foaming agents are roughly classified into the following three types. The first is a solid compound that decomposes at a temperature above the softening point of the resin to generate gas. The second is a liquid or gaseous compound that dissolves in the resin with an affinity and vaporizes in the resin when heated. Third,
It is an inert gas that can dissolve in a resin under pressure. Of these, in the extrusion foaming method, the liquid or gas compound that vaporizes in the second resin was most preferably used, and the third inert gas was used supplementarily.

Liquids or gaseous compounds that vaporize in the resin were also referred to as readily volatile liquids. Easily volatile liquids are divided into aliphatic hydrocarbons such as hexane, pentane and butane,
It contained two types of compounds, halogenated aliphatic hydrocarbons such as methyl chloride and dichlorodifluoromethane.
The inert gas was also simply called a gas and contained carbon dioxide, nitrogen and the like. These foams were to be used as a mixture.

When extrusion foaming was performed by adding the above-mentioned foaming agent to the styrene resin, an extruded foam was obtained. However, in the styrene resin foam thus obtained, the flexural strength and the compressive strength have a contradictory relationship. That is,
There is a relationship that a material having a high compressive strength has a weak bending strength, and therefore becomes buckled even if it is slightly bent, and conversely, if the bending strength is strong, the compressive strength becomes weak. Further, if the bubble diameter was made smaller, it would be less likely to break even when bent, but the compressive strength was weakened. Therefore, the bubbles are small
A foam having a density of 25 to 35 kg / m ³ and having a compressive strength of 2 kg / cm ² or more could not be easily obtained under the condition that the strain of 100% was added.

However, in the case of using styrene resin foam,
As a matter of course, the compressive strength and the bending strength were required to be balanced and excellent. For example, thick styrene resin foam boards have been used in large quantities as core materials for tatami floors. When producing a tatami floor, a plate-like foam having a thickness of 20 to 25 mm was sandwiched between straws having a thickness of about 300 mm and compressed by a roll to a thickness of about 50 mm for sewing. Thus, when compressed by a roll, the foamed plate was broken if the bending strength was weak, and if the compression strength was weak, a floor having a desired thickness could not be obtained. Therefore, even if it is bent to some extent, it can withstand the bending, can easily return to its original state without buckling or breaking even if it is bent, and even if it has a sufficient compression strength even in the bent state, Although a styrene resin foam was required, it was not possible to reliably obtain a foam satisfying this requirement.

The foam obtained by extrusion-foaming a styrene-based resin always had a non-foamed or low-foamed skin on its surface. Therefore, in order to observe the foamed state of the extruded foam, it was necessary to peel off the non-foamed thin skin and observe the foamed state inside. When the conventional extruded foam was observed in this manner, the foamed state was distinct. That is, various bubble states were revealed depending on the molding conditions adopted at the time of extrusion foaming.
For example, when it was strongly stretched in the extrusion direction during extrusion foaming, all the cells were expanded in the extrusion direction. Further, when the tensile force in the extrusion direction was reduced and expanded in the thickness direction as much as possible, the bubbles became elongated in the thickness direction. In the market, various kinds of bubbles are mixedly provided.

(0006) The present invention has a density of a styrene resin extruded foam 25~35kg / m ^2, the bending strength is strong, easily without causing buckling or breakage even when bent In order to provide a foam that can return to its original state, has a large compressive strength in a bent state, and a compressive strength of 2 kg / cm ² or more in a 10% strained state. To do.

(Means for Solving the Problem) The present inventor examined the relationship between the compressive strength and the bending strength in an extruded foam of a styrene resin. As a result, they found that the compromise between compression strength and bending strength was closely related to the state of bubbles in the foam.

Since this styrene resin foam has a thin skin which is not foamed on the surface, the thin skin must be scraped off and the inside thereof must be observed in order to observe the bubble state. As a result of studying the relationship between the state of bubbles inside the foam and the strength in this way, when the shape of the bubbles is in a special state, the foam has both compressive strength and bending strength. It was found that it would be well balanced and good. More specifically, for example, in the case of a styrene resin extruded foam plate having a thickness of 10 to 50 mm and a density of 25 to 35 kg / m ³ , when the thickness of 1 mm is removed as a thin skin portion, bubbles appearing on the surface are extruded. The shape is greatly extended in the direction, but as it approaches the center of the thickness direction, the bubbles gradually become less extended in the extrusion direction, and the bubble diameters in the extrusion direction, the width direction, and the thickness direction become equal. It has been found that, when tending, and preferably with an average cell size of 0.1-0.5 mm, the extruded foam is balanced in both compressive strength and flexural strength. The present invention has been completed based on such knowledge.

(Summary of the Invention) The present invention is a styrenic resin foam with a thin skin made by an extrusion foaming method, having a thickness of 10 to 50 mm and a density of
25~35kg / m ³ and average cell diameter of the extrusion direction in a portion excluding the thickness of 1mm from the skin is greater than the average cell diameter in the width direction and the thickness direction, the ratio is in the range of 1.2 to 2.0 The styrene resin foam is characterized in that the ratio gradually approaches 1 as the ratio approaches the center of the foam in the thickness direction.

(Explanation of each requirement) In the present invention, a styrene resin is used as the resin. The styrene-based resin includes a homopolymer of styrene and a copolymer of styrene and another monomer. Other monomers are, for example, α-methylstyrene, methacrylic acid, acrylic acid ester, methacrylic acid ester, acrylonitrile, butadiene, maleic anhydride and the like. These copolymers contain 50% by weight or more of styrene.

Extrusion foaming is performed as it has been done so far. That is, an inorganic filler such as talc is added to a styrene resin, other stabilizers, pigments, and flame retardants are added, and the above-mentioned foaming agent is pressed into the extruder to form a foam. A conventional extruder can be used as the extruder as it is, a flat die can be used as the die, and a molding tool can be attached to the tip of the die.

This invention has a thickness of 10 to 10 among styrene resin foams.
It is intended for foams of 50 mm and density of 25-35 kg / m ³ . The reason is that it is difficult to accurately grasp the difference in bubbles in the thickness direction with a foam having a thickness of 10 mm or less, and it becomes difficult to adjust the bubbles when the thickness is 50 mm or more. Further, if the density is 25 kg / m ³ or less, it is not valuable as a foam, and if it is 35 kg / m ³ or more, both the compressive strength and the bending strength are insufficient.

Regarding the average cell diameter, the larger the cell diameter, the stronger the compressive strength, but the more easily it breaks when bent, and the smaller the cell diameter, the harder it becomes to break even if it bends, but the lower the compressive strength. In consideration of such a point, in the present invention, the average bubble diameter is 0.1-0.5 mm.

In the present invention, to define the state of bubbles, the portion where a thin skin having a thickness of 1 mm is peeled from the epidermis is used as a reference. This is because the extruded foam has a non-foamed or low-foamed skin on the surface as described above. When the skin is peeled off, the bubbles appearing on the surface need to be stretched particularly long in the extrusion direction.

Specifically, the bubbles appearing on the surface need to have the following relationship. The extrusion direction is MD and the width direction is
If TD and VD in the thickness direction, the average bubble diameter of MD is within the range of 1.2 to 2.0 with respect to the average bubble diameter of TD (MD / TD),
Also, the average bubble diameter of MD is (MD / V
D), needs to be in the range 1.2-2.0.

Further, in the present invention, both the MD / TD ratio and the MD / VD ratio described above need to gradually approach 1 as they approach the center of the foam in the thickness direction. In other words, at the center of the foam in the thickness direction, it means that the cells are not particularly stretched in the extrusion direction and MD approaches TD and VD. . The bubbles in the foam mean that they are close to a sphere, though they are angular and not spherical.

The above relationship will be described more specifically with reference to the drawings.
It is as follows. 1 to 4 are enlarged sectional views of a styrene type resin extruded foam according to the present invention. FIG. 1 is an enlarged cross-sectional view of a foam when a surface of 1 mm in thickness is peeled from the surface to reveal the surface and the surface is cut toward the center in the thickness direction. The horizontal direction in FIG. 1 is the extrusion direction, and the vertical direction is the thickness direction. Since the bubbles in FIG. 1 are stretched in the lateral direction, the average bubble diameter ratio in the extrusion direction and the thickness direction is considered to be 1.5: 1. FIG. 2 is an enlarged cross-sectional view of the foam when the same surface is cut in the width direction from the epidermis toward the center. The horizontal direction in FIG. 2 is the width direction, and the vertical direction is the thickness direction. The bubble diameter in the extrusion direction in FIG. 1 is larger than the bubble diameter in the width direction in FIG.
The average bubble diameter ratio is considered to be 1.2: 1.

FIG. 3 shows a cross-section of the same foam as that shown in FIGS. 1 and 2 when cut in the thickness direction at the central portion in the thickness direction, enlarged to the same magnification as in FIGS. 1 and 2. It is a thing. The horizontal direction in FIG. 3 is the extrusion direction, and the vertical direction is the thickness direction. In FIG. 3, the average diameter of bubbles is 1.06: 1 in the extrusion direction and the thickness direction. FIG. 4 is an enlarged cross-sectional view of the same foam in the widthwise direction at the center in the thickness direction. The horizontal direction in FIG. 4 is the width direction,
The vertical direction is the thickness direction. The bubble diameter in the extrusion direction in Fig. 3 is larger than the bubble diameter in the width direction in Fig. 4, and the average diameter is 1.
The ratio is 1: 1.

5 to 8 are enlarged sectional views of other styrene resin foams according to the present invention. 5 and 6 show
FIG. 3 is an enlarged view of a foam cross section when cut in the thickness direction and the width direction, respectively, in the surface portion after removing the skin, as in FIGS. 1 and 2. The horizontal direction in FIG. 5 is the extrusion direction, and the vertical direction is the thickness direction. In FIG. 5, the average bubble diameter has a ratio of 0.33 to 0.22 in the extrusion direction and the thickness direction. The horizontal direction in FIG. 6 is the width direction, and the vertical direction is the thickness direction. The bubble diameter in the extrusion direction in FIG. 5 is larger than the bubble diameter in the width direction in FIG. 6, and the ratio is 0.33 to 0.20.

Similar to FIGS. 3 and 4, FIGS. 7 and 8 are cross-sectional views taken along the thickness direction and the width direction at the center of the foam in the thickness direction, respectively. It is the figure expanded to the same magnification as the figure. The horizontal direction in FIG. 7 indicates the extrusion direction, and the vertical direction indicates the thickness direction. In FIG. 7, the bubble diameter has a ratio of 0.37 to 0.35 in the extrusion direction and the thickness direction. The horizontal direction in FIG. 8 indicates the width direction, and the vertical direction indicates the thickness direction. The bubble diameter in the extrusion direction in FIG. 7 is larger than the bubble diameter in the width direction in FIG. 8, and the ratio is 0.37 to 0.35.

(Effects of the Invention) The styrene resin extruded foam having bubbles as described above is characterized in that the compression strength is well balanced with the bending strength. This is clear when measuring the compressive strength of the above foam when a strain of 10% is applied. That is, the extruded foam of styrene resin until now, when the compressive strength was measured by applying a strain of 10%, the compressive strength was less than 2 kg / cm ² , but the extruded foam according to the present invention is It has a 10% strain compression strength of ² kg / cm ² or more. Therefore, the foam according to the present invention is a field in which both bending strength and compressive strength are required,
It is a useful material in the field where it is used in combination with the core material of tatami floors, especially straw, and is expected to be used in various fields.

Hereinafter, the reason why the foam according to the present invention is excellent will be specifically described with reference to examples. In the examples below, simply parts or% means parts by weight or% by weight. In addition, the average bubble system is measured by ASTM-D2842-6
Measured by 9.

Example 1 Polystyrene (Vicat softening point 103 ° C., melt index 4.5) was used as a resin, and with respect to 100 parts of this resin,
5.0 parts of fine powder talc having a particle size of 1 to 4 microns, 2 parts of hexabromocyclododecane as a brominated flame retardant, and 0.05 parts of trisnonylphenyl phosphite were added, and this mixture was fed to the extruder.

The above mixture was heated and melted in an extruder to be mixed, and a foaming agent was pressed into the molten resin. Only methyl chloride was used as the foaming agent, and 2.4 mol of methyl chloride was injected under pressure to 1 kg of the resin.

The temperature of the resin was adjusted to 125 ° C. at the outlet of the extruder and extruded from the die. As a base, the tip is 0.5 mm thick and 100 mm wide
Was used, and the resin was extruded from there. A molding tool was closely attached to the tip of the die. The molding tool has an inlet dimension substantially equal to the above-mentioned slit of the die, an outlet dimension of 22 mm in thickness, a width of 200 mm and a total length of 50 mm, and is provided with a resin passage that is gradually expanded from the inlet to the outlet. I used the one. The inside of this resin passage was coated with a fluororesin. Oil at 90 ° C was circulated in the molding tool to cool it. In this way, the resin that came out of the die is guided to the molding tool, and it is taken up while pressing it with a roll to a thickness of 25
An extruded foam plate having a width of 250 mm and a width of about 250 mm was obtained.

The resulting foam plate had a density of 32 kg / m ³ , an average cell diameter of 0.3 mm excluding the skin 1 mm, and the cells immediately below the skin 1 mm had a longitudinal direction (MD) of 0.29 mm and a width direction (TD). Was 0.24 mm and the thickness direction (VD) was 0.19 mm. Therefore, MD / TD = 1.2, MD / VD =
At 1.5, the bubble in the thickness direction center is MD 0.37mm, TD 0.32mm, V
D was 0.35 mm, MD / TD = 1.1, MD / VD = 1.06, and the compressive strength was 2.5 kg / cm ² when 10% strain was applied in the thickness direction after standing for 2 weeks at room temperature. In addition, the thermal conductivity at 20 ℃ is 0.029Kcal / m ・ hr ・ ℃, and it can be processed into a good tatami floor without breaking and buckling in combination with straws, and also as a heat insulating material. It was natural.

Example 2 In Example 1, the average particle size is 1.5 to 1.8 with respect to 100 parts of the resin.
A foam plate was obtained in exactly the same manner as in Example 1 except that 4.0 parts of micronized talc powder was used and methyl chloride was used in an amount of 3 mol per 1 kg of the resin.

The resulting foam plate had a density of 30 kg / m ³ , an average cell diameter of 0.35 mm excluding the skin 1 mm, and the cells immediately below the skin 1 mm were MD / TD.
The ratio of / VD is 0.33 / 0.25 / 0.20, the ratio of MD / TD / VD is 0.37 / 0.35 / 0.35 at the center of the thickness direction, and the strain of 10% in the thickness direction after leaving for 2 weeks at room temperature. The compressive strength when added was 2.4 Kg / m ² . Therefore, as in Example 1, it was recognized that the foam was good as a tatami-bed core material and a heat insulating material.

Example 3 In Example 1, 3.5 parts of fine powder talc was added to 100 parts of the resin.
A foam plate was obtained in exactly the same manner as in Example 1 except that a mixture of 2 mol of methyl chloride and 0.1 mol of nitrogen gas was used as a foaming agent per 1 kg of the resin.

The resulting foam plate had a density of 32 kg / m ³ , an average cell diameter of 0.28 mm excluding the skin 1 mm, and the cells immediately below the skin 1 mm were MD / TD.
The ratio of / VD is 0.33 / 0.28 / 0.21, the ratio of MD / TD / VD is 0.31 / 0.26 / 0.31 at the center of the thickness direction, and the strain of 10% in the thickness direction after leaving for 2 weeks at room temperature. The compressive strength when added was 2.5 Kg / m ² . Therefore, as in Example 1, it was recognized that the foam was good as a tatami-bed core material and a heat insulating material.

Example 4 In Example 1, 2 kg of methyl chloride was added to 1 kg of the resin.
A foam plate was obtained in exactly the same manner as in Example 1 except that 1 mol and 0.2 mol of monochlorodifluoromethane were used.

The foam plate obtained had a density of 29 kg / m ³ , an average cell diameter of 0.31 mm excluding the skin 1 mm, and the cells immediately below the skin 1 mm were MD / TD.
The ratio of / VD is 0.42 / 0.36 / 0.23, the ratio of MD / TD / VD is 0.47 / 0.34 / 0.38 at the center of the thickness direction, and the strain of 10% is applied in the thickness direction after left at room temperature for 2 weeks. The compressive strength when added was 2.0 kg / cm ² , and as in Example 1, the tatami mat core material,
It was recognized as good as a heat insulating material.

Comparative Example 1 In Example 1, 1.0 part of fine powder talc was added to 100 parts of the resin.
A foam board was obtained in exactly the same manner as in Example 1, except that 2 mol of methyl chloride was used per 1 kg of resin as the foaming agent.

The resulting foam plate has a density of 36 kg / m ³ , an average bubble diameter of 0.9 mm in the part where the thin skin 1 mm was peeled off, and the bubbles immediately below the thin skin 1 mm were MD / T.
The ratio of D / VD is 1.0 / 0.9 / 0.6, the ratio of MD / TD / VD in the center of the thickness direction is 1.2 / 1.0 / 0.7, and it is 10% in the thickness direction after left at room temperature for 2 weeks. Compressive strength when strain is applied
It was 1.6 Kg / cm ² . Therefore, this foam has
It was inferior to that of No. 3.

Comparative Example 2 In Example 1, 4.0 parts of fine powder talc having an average particle size of 15 microns was used for 100 parts of resin, and 1 kg of resin was used as a foaming agent.
On the other hand, a foam plate was obtained in exactly the same manner as in Example 1 except that 2 mol of methyl chloride was used.

The obtained foam plate has a density of 33 Kg / m ³ , an average cell diameter of 0.42 mm in the part where the thin skin 1 mm is peeled off, and the bubbles directly below the thin skin 1 mm are MD /
The ratio of TD / VD is 0.4 / 0.25 / 0.18, the ratio of MD / TD / VD in the center of the thickness direction is 0.61 / 0.3 / 0.28, and it is 10% in the thickness direction after being left at room temperature for 2 weeks. The compressive strength when strained was 1.5 Kg / cm ² . Therefore, this foam was inferior to those of Examples 1 to 3.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are enlarged cross-sectional views of the foamed portion of the surface of the foamed body according to the present invention, where a 1 mm-thickness portion is peeled from the skin. FIG. 3 and FIG. 4 are enlarged views of the foam cross section at the central portion in the thickness direction of the same foam. Fifth
FIG. 6 and FIG. 6 are enlarged cross-sectional views of the foamed portion of the surface portion which appears by peeling off a portion having a thickness of 1 mm from the skin of another foamed material according to the present invention. FIG. 7 and FIG. 8 are enlarged views of the foam cross section at the central portion in the thickness direction of the same foam.

Claims (1)

[Claims] 1. A styrenic resin foam with a thin skin, produced by an extrusion foaming method, having a thickness of 10 to 50 mm and a density of
25 ~ 35 kg / m ³ , the average cell diameter in the extrusion direction in the portion excluding the thickness 1 mm from the skin is larger than the average cell diameter in the width direction and the thickness direction, the ratio is within the range of 1.2 to 2.0. A styrene-based resin foam, wherein the value of the ratio gradually approaches 1 as it approaches the center of the foam in the thickness direction.