JPH0768402B2 - Propylene resin foamed particles and foamed molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to expanded particles of a propylene-based copolymer resin and an expanded molded article. The foamed particles of the present invention are filled in the mold cavity of a mold having a steam hole, and the foamed molded product obtained by fusing the foamed particles with each other by heating with steam has a strong fusion of the foamed particles, It has excellent mechanical strength, and is useful as a heat insulating material for hot spring pipes, a heat insulating material for solar water heaters, a heat insulating material for wall materials and floor base materials, and a cushioning material for refrigerators and televisions.

[Conventional technology]

Polystyrene foam is used in a wide range of fields as a heat insulating material and a cushioning material for packaging. However, this polystyrene foam has a low compression strain recovery rate and a heat resistance of at most 70-
80 ℃, poor oil resistance and impact resistance.

Expanded propylene-based resin particles have been proposed as a solution to these drawbacks (Japanese Patent Publication No. Sho 49-2183, Japanese Unexamined Patent Publication No. Sho 57-57).
-90027, 57-195131, 58-1732, 58-238
No. 34, No. 58-25334, No. 58-33435, No. 58-55231
No. 58-76229, No. 58-76231, No. 58-76232,
58-76233, 58-76234, 58-87027, 62
-151325).

Of the propylene-based resin expanded particles, expanded polypropylene-based expanded particles have high-pressure steam (high-temperature steam) in the fusion of the expanded particles during in-mold molding, so that the ethylene content is 1 to 20. Pre-expanded particles using a weight% ethylene / propylene random copolymer as a base resin have been proposed (Japanese Patent Publication No. 59-23731).

This has the advantage that it can be molded with steam at a pressure lower than that using homopolypropylene or ethylene / random block copolymer as the base resin.

[Problems to be Solved by the Invention]

These propylene-based resins are prepared by dispersing propylene-based resin particles in water in a closed container, then supplying a viable organic expander into the closed container, and adjusting the pressure in the closed container to the vapor pressure of the expander or higher. After heating to above the softening temperature of the propylene resin particles while maintaining the pressure of, the temperature and pressure are maintained for a certain period of time, and then the discharge port provided below the water surface in the closed container is opened to contain a volatile expander. The propylene-based resin particles and the water are simultaneously released into an atmosphere at a pressure lower than that in the container to produce the propylene-based resin expanded particles (see the above-mentioned patent publications).

Also in this method for producing expanded particles of propylene-based resin, in order to obtain expanded particles having the same expansion ratio, the filling rate of water, resin, etc. in the container (volume ratio of the content used in the reaction to the volume in the closed container) When the same, the ethylene / propylene random copolymer, which has a lower melting point of the resin, requires a lower heating temperature than homopolypropylene or block copolymer, so the internal pressure of the closed container is small, and the pressure resistance of the closed container is designed. The coefficient of can be reduced.

Among ethylene / propylene random copolymers having the same crystallinity, a copolymer having a high ethylene content has a lower melting point of the copolymer and is therefore preferable in terms of foamability and moldability.

However, a molded product obtained by heat-sealing in a mold using expanded particles using an ethylene / propylene random copolymer as a base resin (for example, bumper core material; JP-A-58-22).
1745), the expansion ratio of the molded product is lowered (JP-A-60-189660), or an ethylene / propylene random copolymer with a low ethylene content is used as the base resin. Must be used.

Taking a bumper core as an example, reducing the foaming ratio (increasing the density) of the molded product (bumper core) increases the weight of the bumper core, which is preferable for vehicle design. Absent.

On the other hand, when an ethylene / propylene random copolymer having a low ethylene content is used as the base resin, it has a high melting point, and as described above, it is necessary to increase the pressure resistance of the closed container for producing the expanded particles and raise the operating temperature. is there. Further, it is disadvantageous from the viewpoint of economical implementation such as equipment and utility such as increasing the mold clamping force of the mold molding machine for heat-sealing the expanded particles.

Further, the cells of the obtained expanded particles become too fine, and the fusion of the expanded particles during molding of the molded product becomes poor.

On the other hand, in JP-A-60-110734, the 1-butene content is 15
-40 mol% (19-47% by weight), latent heat of crystallization 5-15cal / g
Pre-expanded particles of propylene / 1-butene copolymer are described.

The intended place is to apply an internal pressure to the pre-expanded particles with pressurized air, fill the mold with the pre-expanded particles, fill the mold, and heat the secondary foam by heating in the mold to obtain a foaming temperature. It is a decrease, and no knowledge for improving the mechanical strength of the molded body is disclosed.

The 1-butene content of propylene.
As is understood from the low latent heat of crystallization of 5 to 15 cal / g, butene random copolymer has many amorphous parts, so the molding temperature of the molded product can be lowered, but compression of the resulting molded product Strength has little improvement effect.

INDUSTRIAL APPLICABILITY The present invention is capable of producing expanded particles and heat-sealing the expanded particles with an existing apparatus and at a relatively low temperature or a low pressure, and compressing an expanded molded article obtained by heat-sealing the expanded particles. Provided are expanded beads which give excellent strength.

[Specific means for solving the problem]

In the present invention, the 1-butene content is 3 to 12% by weight, preferably 4 to 10% by weight, the latent heat of crystallization is 17 to 25 cal / g, and the bulk density is 0.015 to 0.09 g / cm ^3. In addition to making it possible to lower the foaming temperature and the steam pressure (temperature) during foam molding by using a highly crystalline propylene / 1-butene random copolymer for the production of foam molded articles with compressive strength as the base resin. The compression strength of the obtained foamed molded product was also improved.

That is, the present invention is a propylene-based resin expanded particle for producing a foamed molded product having a high compressive strength using a propylene / 1-butene random copolymer as a base resin, wherein the 1-butene content of the copolymer is Is 3 to 12% by weight, and the latent heat of crystallization is
A 17~25cal / g, and a bulk density of 0.015~0.09g / cm ³
The present invention provides expanded propylene-based resin particles, and an expanded molded article having high compressive strength, which is molded using the expanded particles.

The 1-butene content of this propylene / 1-butene random copolymer is 1 when the copolymer particles are hot pressed at 190 ° C.
Apply a pressure of ² kg / cm ² G per minute to obtain a 0.5 mm thick sheet, and
The sample was left at 1 ° C. for 1 day, and the sample was obtained by infrared absorption spectrum analysis.

In addition, the latent heat of crystallization was measured by a differential scanning calorimeter (DSC) in Sample 3
Heat and melt ~ 8mg at 240 ℃, then 30 ℃ at 10 ℃ / min cooling rate
The exothermic energy generated at the time of crystallization of the melted and cooled copolymer was determined from the peak area on the DSC chart.

The 1-butene content of the copolymer is 3 to 12% by weight, preferably 4 to 10% by weight. A copolymer having a 1-butene content of less than 3% by weight has a finer cell of a foam and a higher melting point, so that the heating temperature or heating pressure for the production of expanded particles and the heat fusion of the expanded particles becomes too high. Will end up. When the 1-butene content exceeds 12% by weight, the foamed molded product is inferior in compression strength and heat resistance.

The α-olefin copolymerizable with propylene is 1
-In addition to butene, ethylene, hexene-1, pentene-1
, Etc., but it seems that 1-butene has a crystal structure close to that of propylene in the copolymer, and therefore the crystal stability is presumed to be high.

The crystal latent heat of the base resin of this propylene / 1-butene random copolymer is 17 to 25 cal / g, and the bulk density of the expanded particles is 0.0
It is 15 to 0.090 g / cm ³ , preferably 0.030 to 0.070 g / cm ³ .

50% by weight for propylene / 1-butene random copolymer
If necessary, it may be blended with another polyolefin resin to the extent that it does not exceed the above range. For example, homopolypropylene, ethylene-propylene random copolymer, ethylene-propylene block copolymer, ethylene-propylene rubber, ethylene-propylene-1-butene random copolymer, high pressure low density polyethylene, straight chain low density Polyethylene, medium / high density polyethylene, ethylene / vinyl acetate copolymer, ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / acrylic acid copolymer and the like may be added.

Further, the resin may contain an inorganic filler such as zeolite, silica or talc, a pigment, a heat stabilizer, a dye, a lubricant or an antistatic agent. These should be 5% by weight or less, preferably 2% by weight or less in order to improve the fusion when the foamed particles are heated with steam and fused to each other to form a molded body.

The weight of one propylene / 1-butene random copolymer particle is 0.01 to 20 mg. For granulation, any method such as strand cutting method, underwater cutting method, sheet cutting method, freeze crushing, and melt spraying method may be used.
Decide in consideration of moldability and quality. Moreover, you may re-granulate.

The expanded particles of propylene / 1-butene random copolymer are produced according to the method described in the above-mentioned patent publications.

For example, propylene / 1-butene random copolymer particles are dispersed in water in a closed container, and then a volatile expanding agent is supplied into the closed container, which is higher than the softening point of the resin particles and is higher than the melting point.
After heating the dispersion liquid to a temperature not higher than 20 ° C., the discharge port provided below the water surface in the closed container is opened, and the water dispersion liquid containing the resin particles impregnated with the expanding agent is pressurized in the closed container. It is manufactured by releasing into a lower pressure atmosphere (in the air). During this production, it is preferable to pressurize with air or nitrogen gas to facilitate the release.

Examples of the volatile expanding agent include aliphatic hydrocarbons such as propane, butane, pentane, hexane and heptane; halogen such as trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane, methyl chloride, ethyl chloride and methylene chloride. Organic compounds having a boiling point of 80 ° C. or lower, such as chemical hydrocarbons, can be used alone or in combination of two or more.

The amount of the volatile expanding agent added varies depending on the type of the expanding agent and the intended bulk density of the resin particles, but is usually 10 to 50 parts by weight with respect to 100 parts by weight of the resin particles.

As the dispersant for dispersing the resin particles in water, inorganic suspending agents such as aluminum oxide, titanium oxide, calcium carbonate, basic magnesium carbonate and tricalcium phosphate; polyvinyl alcohol, methyl carboxycellulose, N
-Water-soluble polymeric protective colloid agent such as polyvinylpyrrolidone; anionic surface active agents such as sodium dodecylbenzene sulfonate, sodium alkane sulfonate, sodium alkyl sulfate ester, sodium olefin sulfate ester, acylmethyl taurine, sodium dialkylsulfosuccinate Agents and the like. Among these, it is preferable to use the inorganic suspending agent having a particle size of 0.01 to 0.8 micron and tribasic calcium phosphate in combination with the suspension aid sodium dodecylbenzenesulfonate. This fine tribasic calcium phosphate contains phosphoric acid for 1 mol of calcium hydroxide.
It is obtained by reacting in water at a ratio of 0.60 to 0.67 mol.

The amount of water as the dispersion medium is 100 to 1,00 per 100 parts by weight of resin particles.
It is 0 part by weight, preferably 200 to 500 parts by weight. If it is less than 150 parts by weight, resin particles are likely to block during heating and pressurization. If the amount exceeds 1,000 parts by weight, the productivity of expanded beads decreases, which is not economical.

A gaseous expander or a liquid expander is supplied to an aqueous dispersion of propylene / 1-butene copolymer resin particles dispersed in water by a dispersion medium, and this aqueous dispersion softens the resin in a closed container. While being heated to a temperature equal to or higher than the point and equal to or lower than 20 ° C. higher than the melting point, the pressure in the container is increased by this heating and the expander is impregnated in the copolymer particles.
Then, the bulk density is 8 to 100 kg / by discharging the copolymer resin particles together with water from the discharge port such as a slit and a nozzle provided in the lower part of the closed container into the low pressure region (generally at atmospheric pressure) from the closed container. It is possible to produce m ³ propylene / 1-butene random copolymer expanded particles.

In the production of the expanded beads, an inorganic gas such as nitrogen, helium or air is supplied into the closed container during or after the expansion agent is added into the closed container to apply pressure.
The inorganic gas may be supplied before heating the dispersion or after heating it.

The supply of an inorganic gas such as air, nitrogen gas or argon into the closed container facilitates the impregnation of the expander into the resin particles, and serves to obtain the propylene / 1-butene copolymer expanded particles having a low bulk density.

The heating temperature of the dispersion liquid is a differential scanning calorimeter of propylene / 1-butene copolymer resin particles, and the peak of crystal melting temperature (so-called melting point) is determined. A temperature within the upper limit of 20 ° C above this peak temperature, preferably 3 above this peak temperature.
A temperature lower by ~ 15 ° C may be selected.

The time for holding the dispersion liquid in the closed container is 30 minutes to 12 hours, preferably 1 to 3 hours, although it depends on the pressure applied, the holding temperature and the target expansion ratio.

The foamed particles released into the atmosphere are dried (cured) in a room at 30 to 65 ° C to remove water adhering to the surface, and then applied to the molding of buffer materials, containers and the like.

As a foam molding method for producing a foam molded article using the obtained expanded particles, various conventionally known methods can be used. An example is shown below.

． After filling the expanded beads into the mold, increase the volume of the expanded beads to 15
A compression molding method (DOS2107683) to obtain a product by compressing so as to reduce by -50%, then introducing 1-5 kg / cm ² G of steam to fuse the expanded particles together, and then cooling the mold.

． The mold is filled with pre-expanded particles obtained by impregnating the expanded particles with a volatile liquid expander in advance and imparting the secondary expandability to the expanded particles, and heating with steam to perform secondary expansion and fuse the particles together. To get the product.

． The expanded particles were placed in a closed chamber, and then an inorganic gas such as air or nitrogen gas was pressed into the chamber to increase the pressure in the cells of the expanded particles to impart secondary foamability, and to impart this secondary foamability. A method in which pre-expanded particles are filled in a mold, heated with steam to perform secondary expansion, and the particles are fused together to obtain a product. (Japanese Patent Publication No. 59-23731).

． In the mold pressurized to 1.0 to 6.0 kg / cm ² G with a pressurized gas, the expanded particles are compressed using a pressurized gas that is 0.5 kg / cm ² or more higher than the in-mold pressure and divided into multiple times. Then, the pressure in the mold is continuously maintained at the pressure in the mold during the filling, and after the completion of the filling, the pressure in the mold is returned to the atmospheric pressure, and then the heating is performed so that the foamed particles are separated from each other. Fuse,
Formula of foamed particles in that case [In the formula, W, V and σ represent the following, respectively.

W: Weight of molded product (g) V: Volume of molded product () σ: Bulk density (g /) of expanded particles in air] A method of controlling the compressibility to 40 to 70%. (JP-A-62-151325). Obtained by pressurizing for 1 hour or more using a pressurizing gas that is 0.5 kg / cm ² or more higher than the in-mold pressure in a mold that has been pressurized to 0.5 to 5.0 kg / cm ² G with a pressurizing gas. The expanded particles to which the gas internal pressure is applied are divided into a plurality of times using a pressurized gas having a pressure higher by 0.5 kg / cm ² or more than the above-mentioned pressure in the mold and sequentially filled, and the pressure in the mold is increased during the filling. The above-mentioned in-mold pressure is continuously maintained, and after the completion of filling, the in-mold pressure is returned to atmospheric pressure, and then the above heating is performed to fuse the expanded particles, and the expression of the expanded particles at that time [Equations, W, V and σ represent the following, respectively.

W: Weight of molded product (g) V: Volume of molded product () σ: Bulk density (g /) of foamed particles in air (g /)] Reduce compression rate to less than 40% (excluding 0%) How to control.

The foamed molded product of the propylene / 1-butene copolymer molded in this manner has excellent fusion between the foamed particles and has high mechanical strength.

Hereinafter, the present invention will be described in more detail with reference to Examples. The parts and% in the examples are based on weight.

Example 1 1-butene content 6.0% by weight, MFR 8.5 measured at 230 ° C.
g / 10 minutes, propylene / 1-butene random copolymer particles with a latent heat of crystal of 19.6 cal / g (the average weight of one particle is about 1 m
g) was used to obtain expanded particles.

That is, 250 parts of water, the propylene
100 parts of 1-butene copolymer particles, 1.0 part of tribasic calcium phosphate having a particle size of 0.3 to 0.5 micron, and 0.007 parts of sodium dodecylbenzene sulfonate (filling rate 62%) were charged, and then nitrogen gas was added under stirring to the internal pressure of the closed container. Was increased to 5 kg / cm ² G and the supply of nitrogen gas was stopped. Then, 18 parts of isobutane was fed into a closed container, heated to 132 ° C. over 1 hour, and kept at the same temperature for 45 minutes. The autoclave internal pressure was 24 kg / cm ² G.

After that, open the valve of the discharge nozzle at the bottom of the closed container,
The dispersion was discharged to atmospheric pressure in about 2 seconds to effect foaming. The internal pressure of the closed container at the moment when the final portion after dispersion was released from the closed container was about 10 kg / cm ² G. Also, the temperature of the closed container was maintained at 132 ° C. during the discharge of the dispersion liquid.

The expanded particles of the propylene / 1-butene copolymer thus obtained had a bulk density of 30 kg / m ³ , a particle size of 3.3 mm, and an expanded cell diameter of 150 μm. Moreover, the blocking of foamed particles was not found.

The foamed particles are left to dry in a room at 40 ° C for 2 days, then filled in a mold having steam holes, the foamed particles are compressed by 50%, and then 3.0 kg / cm ² G of steam is introduced, Foamed particles are heated and fused together, then cooled in water for 10 seconds and allowed to cool for 30 seconds, then the molded product is taken out from the mold and has a density of 60 kg / m ³ , vertical 150
A foamed molded product having a size of mm, a width of 300 mm, and a thickness of 12.5 mm was obtained.

The compression strength of this foamed molded product was evaluated by the following measuring method, and was found to be 6.3 kg / cm ² .

A test piece with a density of 60 kg / m ³ and a sample shape of 50 mm × 50 mm × 50 mm is compressed by a method according to JIS-K6767 (compression speed 10
mm / min), compressive strain at 50% compression strength (measured at 20 ° C).

Examples 2 to 4, Comparative Examples 1 to 10, 13 and 14 Using the resins shown in Table 1 as the resin particles, the temperature of the closed container was changed so that the bulk density of the expanded particles would be 30 kg / m ^3. A foamed molded product having a density of 60 kg / m ³ was obtained in the same manner as in Example 1 except that the steam pressure at which the foamed particles were fused together was changed.

The results shown in Table 1 were obtained.

In Table 1, the evaluation of the foaming temperature is the heating and holding temperature in the closed container for obtaining the foamed particles having the bulk density of 30 kg / m ³ when operated under the charging conditions (filling rate) of Example 1.

The molding temperature is the minimum steam pressure required to obtain an excellent foamed molded product.

Comparative Examples 11 and 12 The resin shown in Table 1 was used as the resin particles, and the temperature of the closed container was changed so that the bulk density of the expanded particles became the value shown in the table (therefore, the pressure inside the closed container was also different). Foamed particles were produced.

After applying the internal pressure to the foamed particles under a nitrogen pressure of 2.0 Kg / cm ² G for 24 hours, the foamed particles are filled in a mold having steam holes, and then steam having a predetermined pressure is introduced to heat the expanded particles. After fusion-bonding, followed by water cooling for 10 seconds and cooling for 30 seconds, the molded product was taken out of the mold to obtain a foamed molded product having a length of 150 mm, a width of 300 mm and a thickness of 12.5 mm. Then, the foamed molded product was evaluated in the same manner as in Example 1 and the results shown in Table 1 were obtained.

In Table 1, the evaluation of the foaming temperature is the heating and holding temperature in the closed container, and the molding temperature is the minimum steam pressure required to obtain an excellent foamed molded product.

Example 5 1-Butene content is 5.2% by weight, MFR measured at 230 ° C. is 9.7
g / 10 minutes, propylene / 1-butene random copolymer particles with a latent heat of crystal of 22.6 cal / g (the average weight of one particle is about 1 m
g) was used to obtain expanded particles.

That is, 250 parts of water, the propylene
100 parts of 1-butene copolymer particles, calcium pyrophosphate
1.0 part and 0.007 part of sodium dodecylbenzenesulfonate were charged (filling rate 62%), and then nitrogen gas was pressurized under stirring until the internal pressure of the closed container reached 5 kg / cm ² G, and the supply of nitrogen gas was stopped. Then, 18 parts of isobutane was supplied into a closed container, heated to 140 ° C. over 1 hour, and kept at the same temperature for 45 minutes, and the internal pressure of the autoclave was 26 kg / cm ² G.

After that, open the valve of the discharge nozzle at the bottom of the closed container,
The dispersion was discharged to atmospheric pressure in about 2 seconds to effect foaming. The internal pressure of the closed container at the moment when the final portion after dispersion was released from the closed container was about 10 kg / cm ² G. Also, the temperature of the closed container was maintained at 140 ° C. during the discharge of the dispersion liquid.

The expanded particles of the propylene / 1-butene copolymer thus obtained had a bulk density of 30 kg / m ³ , a particle size of 3.3 mm, and an expanded cell diameter of 150 μm. Moreover, the blocking of foamed particles was not found.

The foamed particles are left to dry in a room at 40 ° C for 2 days, then filled in a mold having steam holes, the foamed particles are compressed by 50%, and then 3.0 kg / cm ² G of steam is introduced, The foamed particles were heated and fused together, then cooled in water for 10 seconds and allowed to cool for 30 seconds, then the molded product was taken out from the mold and had a density of 0.062 g / cm ³ , vertical.
A bumper core material of 1500 mm, width 200 mm, and thickness 150 mm was obtained.

A test piece measuring 80 mm in length, 80 mm in width, and 50 mm in height was cut out from this bumper core material, and the stress / strain curve at 20 ° C and 80 ° C was obtained.
The stress at the time of% strain (compression speed 20 mm / min), the energy absorption efficiency, the energy absorption amount, and the energy absorption ratio between 20 ° C and 80 ° C were obtained.

The results are shown in Table 2.

Examples 6 to 8 and Comparative Examples 15 to 17 Polypropylene resins shown in Table 2, namely, propylene / butene-1 random copolymer (BPF), propylene / ethylene random copolymer (EPF), propylene / ethylene block. Using the copolymer (EPB), a bumper core material having the physical properties shown in Table 2 was obtained according to Example 5.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Goto 1000, Kawajiri-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Verditshie Co., Ltd. (56) Reference JP-A-61-118435 (JP, A)

Claims (2)

[Claims] 1. A propylene-based resin expanded particle for producing a foamed molded product having a high compressive strength, which comprises a propylene / 1-butene random copolymer as a base resin.
A butene content of 3-12% by weight and a latent heat of crystallization of 17-
25 cal / g and a bulk density of 0.015 to 0.09 g / cm ³ expanded propylene resin particles. 2. A foamed molded product having a high compressive strength, which is molded using the expanded propylene resin particles according to claim 1.