JPH03182529A - Expandable resin composition and expanded molding thereof - Google Patents

Abstract

PURPOSE:To obtain an expandable resin composition which can show good retentivity of a blowing agent in the production of a foam and can easily give a highly expanded molding by mixing a copolymer resin obtained by hydrogenating a block copolymer of a vinylaromatic compound with a conjugated diene with a high-impact polystyrene resin. CONSTITUTION:An expandable resin composition formed by mixing a copolymer resin which is a block copolymer of a vinylaromatic compound with a conjugated diene compound wherein most of the double bonds derived from the conjugated diene are hydrogenated with a high-impact polystyrene resin. A preferred composition is one having a total rubber component of 10-25wt.% based on the total resin. A preferred high-impact polystyrene resin is one having a rubber component content of 3-15wt.%, though it is not particularly limited. The above copolymer resin is preferably one which has a vinylaromatic compound content of 20-80wt.% and a degree of saturation of the double bonds derived from the conjugated diene >=80%.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a resin composition useful for foaming applications, particularly in-mold foam molding, and a foam made from the composition, particularly for use in cushioning packaging. This invention relates to a useful foam molded article.

[Conventional technology]

It is widely known that molded objects obtained by molding polystyrene foam beads are easily broken. Several attempts have been made to improve the breakability and poor compressive strain recovery properties of styrene foam bead moldings.

For example, (1) - for boat fishing, a method of adding crack-resistant polyethylene resin or butadiene rubber to polystyrene resin and mixing by a mechanical method to obtain a foaming resin composition, (2) Japanese Patent Publication No. 51-46536 , Japanese Patent Publication No. 55-52331
In the publication, high impact polystyrene resin (hereinafter referred to as
(3) JP-A-54-154471, JP-A-Sho 5
No. 4-158467 discloses polystyrene resin or HI
Method for obtaining a foaming resin composition by mechanically mixing a PS resin and a block copolymer resin of styrene and butadiene (hereinafter referred to as SB resin), (4) JP-A-11-1989
No. 9563 and Japanese Unexamined Patent Publication No. 57-1.11330 disclose a resin composition for foaming using a graft polymer resin of polyethylene resin or a copolymer resin of ethylene and vinyl acetate (hereinafter referred to as EVA resin) and polystyrene. It describes how to obtain things.

[Problem to be solved by the invention]

However, in the above method (1) of mixing polystyrene resin with resin with high crack resistance such as polyethylene resin or butadiene rubber to obtain a foaming resin composition, the resin to be added has different thermal properties from the polystyrene resin. In addition, as a result of the poor mixability and the inability to obtain a homogeneous mixed composition, when this foaming resin composition is impregnated with a volatile organic blowing agent by the method described below to form a foamable resin composition, it has an extremely high There was a problem in that the foamability was poor and a foamed molded product with a high magnification required for a cushioning packaging material could not be obtained. In addition, in the method (2) above for obtaining a foaming resin composition using a HIPS resin, it is known that HIPS resin alone exhibits high cracking resistance in the - grade. The foamed molded product obtained in the above was not completely satisfactory as it did not necessarily have the high cracking resistance that can be seen with HIPS resin alone.

In addition, regarding the relationship between the amount of resin components in He's resin and cracking resistance, it is well known that increasing the amount of rubber components improves cracking resistance, but HIPS resin has a Generally, the maximum amount of butadiene that can be added is approximately 15% by weight based on the total HIPS resin, and for this reason as well, there is a limit to the improvement in cracking resistance.

Furthermore, in the method of (3) above, in which HIPS resin is mechanically mixed with SB resin, which has higher cracking resistance, the rigidity of the added SB resin itself is extremely low. The problem was that I couldn't be satisfied. Furthermore, in the method for obtaining a foaming resin composition using a graft polymer resin of polyethylene resin or EVA resin and polystyrene as described in (4) above, the cracking resistance of the resulting foamed molded product is required to be at a target level. If you try to increase it, polyethylene resin and EV
It is necessary to make the amount of olefin components such as resin A at a high ratio of at least 30% by weight to the total resin amount, and this foaming resin composition is impregnated with a volatile organic blowing agent by the method described below to create a foamable resin composition. When foamed particles are obtained using the method described below, the retention of the blowing agent is extremely low, making it difficult to obtain a foamed molded product with stable quality, and the proportion of the olefin component, which has low mechanical strength properties, is There was a problem that the compressive strength properties of the obtained foamed molded product were low because of the high content.

Therefore, the present invention is intended to solve all of the above-mentioned drawbacks, and the purpose of the present invention is to create a resin composition that has excellent foaming agent retention properties and is easy to form into a foam molded product with high foamability. The purpose of the present invention is to provide a foamed product having excellent compressive strength, cracking resistance, and compressive strain recovery properties when used as a foamed product for use in shock-absorbing packaging.

[Means to solve the problem]

The present invention is a block copolymer of a vinyl aromatic compound and a conjugated diene compound, in which most of the double bonds derived from the conjugated diene are hydrogenated and saturated (hereinafter referred to as H3B resin). ) and a HIPS resin, and a foamed molded product made by fusing and integrating a large number of foam particles made of a mixed resin composition of a HIPS resin and an H3B resin at the surface layer thereof. It is.

Hereinafter, the present invention will be explained in detail using drawings and the like.

The main point of the present invention is to use a mixture of HIPS resin and H3B resin.

[For production]

FIG. 1 is an experimental diagram clearly showing the significance of using the resin composition of the present invention. That is, the horizontal axis in FIG. 1 indicates the amount of the total rubber component relative to the total resin amount in weight percent. This meaning is that in mixing HIPS resin and HSB resin, each of which contains a rubber component, the total rubber amount represents the mixing ratio.

The vertical axis is [foaming agent retention time], [compressive strain recovery amount], [
Evaluation from three viewpoints of compressive strength] is shown below. That is,
According to Figure 1, [compressive strength] and [blowing agent retention time]
It is shown that the ratio decreases as the total amount of rubber components increases, and becomes significantly worse when the total amount of rubber components exceeds 25% by weight. However, it has been shown that [compressive strain recovery amount] decreases as the total rubber bottom content decreases, contrary to the above two items, and further deteriorates significantly when the total rubber content is less than 10% by weight. It can be seen that a composition with improved properties can be obtained. From the point of view of trying to simultaneously satisfy the three properties of [compressive strength], [foaming agent retention time], and [compressive strain recovery], which show contradictory properties in relation to the total rubber component amount, It is desirable to select a composition within the range of the dotted line shown in FIG. 1, that is, the total amount of rubber components in the range of 10 to 25 weight percent.

Figure 2 shows H3B in the total rubber component in the resin composition of the present invention.
It is an experimental diagram showing the significance of the amount occupied by the rubber component of the resin.

That is, the horizontal axis in Fig. 2 shows the amount of the rubber component of the HSB resin relative to the total rubber component amount in weight percent, and the vertical axis shows the evaluation from two viewpoints: [cracking amount] and [expansion ratio]. . According to this Figure 2, as the rubber amount of H3B resin in the total rubber amount decreases, the [foaming ratio] improves, especially H3B resin.
It is shown that when the amount of rubber component in the 3B resin is less than 10% by weight, it is significantly modified. On the other hand, [amount of cracking]
Contrary to the above-mentioned [expansion ratio], the ratio deteriorates significantly as the amount of rubber component of the H3B resin decreases, and in particular, when the amount of rubber component of the H3B resin is less than 10% by weight, it becomes an extremely large value and deteriorates.

That is, it can be seen that improvements in accordance with the target can be extracted by the ratio of the amount of H3B rubber component to the total amount of rubber component in the composition. In this way, from the viewpoint of simultaneously satisfying the two contradictory properties of [expansion ratio] and [cracking amount] in relation to the rubber amount of H3B resin, the range indicated by the dotted line in Figure 2, that is, H5B It has been found that it is desirable to adjust the amount of rubber component in the resin to be in the range of 10 to 60 percent by weight based on the total amount of rubber.

As mentioned above, according to the foam molded article of the foamable resin composition of the present invention, even if the total amount of rubber components in the total amount of resin is small, it has extremely high [cracking resistance] and excellent [compressive strain recovery]. ]
The effect of obtaining a product having the following properties was investigated. Although the mechanism by which such an effect occurs is not necessarily clear, it is thought to be as follows. In other words, the HIPS resin and HSB resin that make up the zero-foamed resin bottom are highly compatible with each other and mix well and homogeneously; ■The main component of the flPs resin itself has high rigidity and crack resistance. thing. ■The H3B resin used has extremely high cracking resistance. HIPS resin and H3B with these properties
It is believed that this is a synergistic effect brought about by homogeneous mixing of the resins.

Next, Table 1 shows the significance of employing HIPS resin and H3B resin in the present invention. Furthermore, the results clearly demonstrate the effects of the present invention in comparison with the prior art. That is, according to the resin composition of the present invention and the foamed molded product obtained therefrom, as seen in Example 1, those that were evaluated as extremely poor in all evaluation items (indicated by an x in the table) were It shows excellent performance over a wide range of the ratio of the total rubber component to the total resin amount.

This indicates the fact that, practically, it is desirable to select the ratio of the total rubber component to the total resin amount from a range of 10 to 25 weight percent.

The HIPS resin used in the present invention is not particularly limited, and the amount of rubber components generally used is the total HIPS resin.
The H3B resin used preferably has a total H3B content of 3 to 15 weight percent based on the amount of resin.
The amount of vinyl aromatic compound component in the amount of 3B resin is 20
~80% by weight and the degree of saturation due to hydrogenation of double viscosity originating from a conjugated diene is preferably 80% or more, more preferably 90% or more. If the amount of the aromatic compound component is less than 20% by weight, mixing with the HIPS resin will be poor and it will be difficult to obtain a homogeneous mixture, and if the amount of the vinyl aromatic compound component exceeds 80% by weight, expensive 1(
The amount of SB resin added increases, which is disadvantageous in terms of cost.

Furthermore, if the degree of saturation of the conjugated diene compound component to be hydrogenated is less than 80 percent, the rigidity of the resulting H3B resin will be slightly inferior, resulting in a decrease in compressive strength when formed into a foam molded product.

In the present invention, "total rubber component amount relative to total resin amount" and "
The rubber component amount of H3BfJ fat in the total rubber component amount is
It can be adjusted by changing the types of HIPS resin and H3B resin used and their formulation.

In the present invention, after HIPS resin and H3B resin are blended in the desired ratio, they are continuously fed to an extruder, where they are homogeneously mixed while being heated and melted in the extruder. After extruding it, it is immediately cooled in a cooling bath filled with water, sandwiched between upper and lower drive rolls, and cut lengthwise with a rotary cutter to obtain a particulate foaming resin composition. .

Further, the method for obtaining a foamed molded article from the foamable resin composition of the present invention is as follows. That is, the particles of the foamable resin composition are obtained by impregnating the foamable resin particles with a volatile organic foaming agent such as pentane, butane, monochlorodifluoroethane, or the like. The method of impregnating the volatile organic blowing agent is, for example, by placing the particles of the foaming resin composition in an autoclave, adding the volatile organic blowing agent to the autoclave, sealing it, and impregnating it by heating and pressurizing it. Alternatively, after the particles of the foaming resin composition are heated and melted in an extruder, a volatile organic foaming agent is separately press-injected through a foaming agent supply line leading to the extruder, and the volatile organic foaming agent is thoroughly mixed with the molten foaming resin composition. After that, it is extruded into a thread form through the pores provided in the goo part of the extruder, and while it is cooled directly in a cooling bath filled with water, it is sandwiched between upper and lower drive rolls and taken out, while being cut lengthwise with a rotary cutter. A method of cutting and obtaining particles of the foamable resin composition is used.

Next, the particles of the foamable resin composition are heated and foamed using steam in a known foaming machine for polystyrene foam beads to form foamed particles. The expansion ratio of the resulting foamed particles is determined by automatically supplying steam when the foamable resin particles expand to a target volume in the foaming machine, relative to the weight of the particles of the foamable resin composition charged into the foaming machine. This is to stop foaming and obtain the target foaming ratio.

Further, the obtained expanded beads are fused and integrated into a single piece using a known automatic molding machine for polystyrene expanded beads to obtain a expanded molded product.

〔Example〕

Next, the present invention will be explained with reference to Examples.

Note that the measurement methods and evaluation methods in the following Examples and Comparative Examples are as follows.

<Measurement method> Weigh foamed particles with an expansion ratio of approximately 5g to the second decimal place to determine the accurate weight (W>.Next, pour approximately 50 to 100cc of water into a glass measuring cylinder whose minimum scale unit is lcc. In addition to this, there is a circular wire mesh plate whose tip is slightly smaller than the diameter of the female cylinder, and in the center there is a wire mesh plate with a length of approximately 15 to 15 mm.
A 30 cm wire is fixed to the upright foam bead pressing tool, and the water level (Vo) at that time is read.

Next, the foamed particles whose weight had been confirmed with the pressing tool removed were placed in a graduated cylinder and completely submerged in water using the pressing tool, and the water level (V) was again read to determine the foaming ratio.

The upper part of the foamable resin particles with a foaming agent content of approximately 5g is weighed to two decimal places and the size and shape are as follows.
Low area 78.5cn! Transfer it to a cylindrical glass container with a height of 10 cm, and weigh it in the same way to two decimal places to confirm the weight. Further, the resin particles were added together with the glass container to 100%
Place in a vacuum deaerator controlled at ℃ -700 vacuum degree
After degassing under 11 g of mm for 60 minutes, the sample was taken out and allowed to cool for 5 minutes in a room, and then weighed to two decimal places to determine the weight as shown below.

G: Blowing agent content (g/100g resin) Weight of GO Ni glass container (g) G1: Total weight of initial glass container and sample (g) G2: Total weight of glass container and sample after vacuum degassing (
g) G+'Ly.

Crack amount J I 5-Z-0235, 3rd grade according to drop impact test method
As shown in the figure, from a height of 60 cm from the top surface of the plate-shaped foamed molded body 1 whose thickness dimension ■ is 5 cm, the wooden shaped rectangular parallelepiped drop impact body 2, which is integrated with the weight 3, is dropped into a plate-like shape. The foamed molded product 1 fell approximately at the center in the length direction and over the entire width in the width direction, and the relationship between the maximum compressive strain of the plate-shaped foamed molded product 1 that occurs at this time and the crack size ■ was determined. . Furthermore, in order to clarify these relationships, the maximum compressive strain amount was plotted on the horizontal axis, and the crack size (■) was plotted on the vertical axis, and they were arranged on a graph.

Next, from the obtained graph, the crack size when the maximum compressive strain amount was 60 percent with respect to the original thickness size (■) of the plate-shaped foam molded product 1 was determined, and the amount of crack was determined as follows.

S: Amount of cracks (%) H: Crack size (cm) T: Thickness size of plate-shaped foam molded product (cm) S=X
100 Pressure j So ■ Side viewing amount According to JIS K-6767 cyclic compression set test method, length x width x thickness dimensions are each 50 mm x 50 mm x
A 25% compression test was performed on a 50 mm specimen, and the results were determined as follows.

R: Recovery amount of compression set (Kaku) RI: Thickness dimension at 25% compression (mm) R2: Thickness dimension after recovery (mm) R=R, -R.

Based on the pressure box 5 degree JIS Z-0234 compression test method, length x width x thickness dimensions are 100mm x 100mm x 50+nn+.

The compressive stress value (kg
/cn) is the compressive strength.

<Evaluation method>'t A) Particles of a foamable resin composition obtained by impregnating 10 g of pentane as a blowing agent into 100 g of resin using a foaming machine for foaming bead polystyrene (manufactured by Sekisui Koki Seisakusho Co., Ltd., 5KK-50).
) for 50 seconds at a steam temperature of 98°C, then
After drying in a drying oven at 0° C. for 20 minutes, the foaming ratio was confirmed using the foaming ratio measuring method, and was determined as follows.

[Evaluation scale]

The same foamable resin particles used in the evaluation section of high foaming performance were made into 30 times larger foam beads using a foaming machine for foamed bead polystyrene (5KK-50, manufactured by Chiboku Kotane Seisakusho Co., Ltd.). The foamed particles are left in a container at room temperature from which humidity has been almost completely removed using a dryer for approximately 24 hours, and after almost completely removing moisture on the surface and inside of the foamed particles, the particles are taken out and the foaming agent content is immediately reduced. The blowing agent content was determined by the measuring method. Furthermore, the blowing agent content was confirmed in the same manner every 3 hours, and the relationship between the standing time and the blowing agent content was shown.
The time required to reduce the amount by half to 0g resin) was confirmed, and the foaming agent retention performance was determined as follows.

[Evaluation scale]

The same foamed particles used in the evaluation of foaming agent retention performance above were used to form a plate-shaped foamed product (length x width x thickness) using an automatic bed forming machine for foamed beaded polystyrene (manufactured by Kasahara Kogyo ■, PIONY-75). Dimensions are 300mm x 300mm x
50 mm and a bulk density of 25 kg/m"), and
The amount of cracking was determined as follows using the measurement method.

[Evaluation scale]

The compressive strength of the same foamed molded product used in the evaluation of crack resistance performance was determined as follows using the method described above.

[Evaluation scale]

Compressive Strain Recovery Performance (Effect E) Using the same foamed molded body as used in the evaluation of cracking performance, the compressive strain recovery was determined as follows using the method described above.

[Evaluation scale]

Comprehensive Evaluation Example 1 In this experiment, when a foamable resin composition was obtained by impregnating a foamable resin composition in the present invention with a volatile organic blowing agent, the resulting foamable resin composition showed high foaming performance. The purpose of this study is to prove that foam molded articles obtained from these expandable resin particles have excellent cracking resistance, compressive strength characteristics, and compressive strain recovery.

HIPS resin [manufactured by Asahi Kasei Corporation, product name: Styron]
HIPS) and H3B resin (manufactured by Asahi Kaei Kogyo ■, trade name: Toughtic) whose saturation degree of the conjugated diene compound component to be hydrogenated is 99 percent or more were made into compositions corresponding to the experiment numbers in the order of experiment numbers. After mixing each resin well with a drum blender, the mixed resins are individually melted and kneaded in an extruder, extruded into threads through the pores in the die, and immediately put into a cooling bath containing cooling water. While being cooled through the medium, the mixture was sandwiched between upper and lower drive rolls, and then cut in the length direction with a rotary cutter to obtain particles of a foamable resin composition. Next, these particles are separately placed in the order of the experiment number with a pressurized blowing agent supply device, and the connection line from the pressurized feed device is connected to the inside of the extruder cylinder and the melt-kneading section. The resin is fed to an extrusion impregnation device equipped with a resin cooling device and a Goo device with a large number of resin outflow holes in the head, and while melting and kneading in the extruder, pentane is added from the blowing agent pressurized feeding device to 100% resin by weight. 10 parts by weight with a pump, and while kneading and mixing with the resin, cooled to an appropriate temperature in a cooling device, extruded into thread form from a number of pores provided in the Gui device, and immediately, The material was passed through a cooling bath containing water at about room temperature and then taken between two drive rolls (upper and lower) and cut lengthwise with a rotary cutter, resulting in a diameter of approximately 1.0 m and a length of 4.0 m. Particles of a foamable resin composition of 0 In were obtained. From these particles of the foamable resin composition, particles of the foamable resin composition and a foamed molded article were obtained by the method described above and evaluated. The evaluation results are shown in Table 1.

Comparative Example 1 Polystyrene resin [manufactured by Asahi Kakai Kogyo ■, trade name: Stylon GP-6803] and polyethylene resin [manufactured by Asahi Kasei Kogyo ■, Santic LD-2115] were blended into compositions corresponding to the experiment numbers shown in Table 2. Particles of a foamable resin composition were obtained in the same manner as in Example 1, except for the following steps, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

Comparative Example 2 HIPS resins (manufactured by Asahi Kakai Kogyo, trade name: Styron) (IPS) containing butadiene bottom valves corresponding to the experiment numbers shown in Table 2 were prepared, and HIPS resins identical to those in Example 1 were prepared. Particles of a foamable resin composition and a foamed molded article were obtained by the method, and evaluated in exactly the same manner as in Example 1. The evaluation results are shown in Table 2.

Comparative Example 3 HIPS resin [manufactured by Asahi Kakogyo ■, product name: Styron-
HIPS, rubber component content 7% by weight] and SB resin [manufactured by Asahi Kakai Kogyo ■, trade name: Toughblane, rubber component content 50% by weight] were respectively added to the composition ratios corresponding to the experiment numbers shown in Table 2. Particles of a foamable resin composition and a foamed molded article were obtained in exactly the same manner as in Example 1.
It was evaluated using exactly the same method. The evaluation results are shown in Table 2.

Comparative Example 4 EVA resin [manufactured by Mitsui Polychemical ■, trade name: Evaflex P-607] particles, water, magnesium carbonate, and seek mill peroxide were blended as follows to obtain a blending intermediate liquid.

Mixing ratio of compounding intermediate liquid EVA resin 1,000 parts by weight water
2.000 Magnesium carbonate 5 Sicumyl peroxide 10 F deciS < 7 tons Sodium acid 1 Next, benzoyl peroxide was added in advance to 2,016 parts by weight of the above blended intermediate solution at a concentration of 1% by weight. The styrene monomers obtained by adding and dissolving the styrene monomers were each blended as follows to obtain three types of blended liquids.

After that, each of the above-mentioned compounded liquid 21 was added for 5I! After the autoclave was sealed, the temperature was raised while stirring, and the temperature was maintained at 70°C for 5 hours to impregnate the resin particles with styrene. 30
At the same time as the styrene polymerization reaction, styrene and E
After the bonding reaction with the VA resin and the crosslinking reaction of the EVA resin were performed, the mixture was cooled and the styrene-EVA copolymer resin particles were taken out.

The amount of styrene contained within these resin particles was 83.75.70 weight percent, respectively. The method for determining the amount of styrene is to determine the amount of styrene remaining in the liquid that remains in the autoclave after the reaction is completed, and then determine the amount impregnated into the EVA resin based on the difference from the amount of styrene added before the reaction. I can do it. Furthermore, each styrene-EVA
2.000 g of copolymer resin particles were placed in 51 pressure-resistant containers, heated under pressure at 80°C in a pentane-filled liquid, and the resin 1
After impregnating approximately 15 parts by weight of pentane per 00 parts by weight, the resin particles were cooled and taken out to obtain expandable resin particles. Next, these foamable resin particles are left at room temperature to dry while the blowing agent is dissipated and reduced, and the blowing agent content is checked periodically using the blowing agent content confirmation method described above. When the agent content reaches IO parts by weight per 100 parts by weight of resin,
Evaluation was made in the same manner as in the examples. The evaluation results are shown in Table 2.

Comparative Example 5 Expandable resin particles were obtained from polystyrene resin [manufactured by Asahi Kakogyo@, trade name: Stylon GP-680] in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

〔Effect of the invention〕

By having the above structure, the present invention has the effect that, when viewed as a resin composition, it has excellent retention of a foaming agent when it is intended to be made into a foam, and it is easy to obtain a highly foamed molded product. In addition, when viewed as a foam molded product obtained, it has the advantage of having excellent cracking resistance, compressive strength characteristics, and compressive strain recovery, and is excellent for use in cushioning packaging.
For example, it can be used for cushioning packaging of lightweight and easily damaged contents such as electronic parts, audio equipment, communication equipment, etc., and is an excellent invention that plays a large role in industry.

[Brief explanation of drawings]

FIGS. 1 and 2 are experimental diagrams showing the content of the invention. Figure 3 is a diagram showing the cracking test method, Figure 3 (A) is a front view when the weighted drop impact object is dropped, and Figure 3 (B) is a diagram showing the cracking test method.
The figure is a front view of a test piece after conducting a cracking test. In Figure 3,
■ indicates the foam molded product, 2 indicates the drop impact body, 3 indicates the weight, 4 indicates the crack in the foam molded product, ■ indicates the crack size (ml), and ■ indicates the thickness (mark) of the foam molded product. Rubber component V of HSB Amount of total rubber composition 3rd (B)

Claims (1)

[Claims] 1. A copolymer resin that is a block copolymer of a vinyl aromatic compound and a conjugated diene compound, in which most of the double bonds derived from the conjugated diene are hydrogenated and saturated, and high impact polystyrene. A foaming resin composition made by mixing with resin. 2. A mixed resin composition of a block copolymer of a vinyl aromatic compound and a conjugated diene compound, in which most of the double bonds derived from the conjugated diene are hydrogenated and saturated, and a high impact polystyrene resin. A foamed molded product made by integrating a large number of foamed particles made of a material by fusing them together on the surface.