JPH11152359A - Extruded propylene-based resin foam and method for producing the same - Google Patents

Abstract

(57) [Abstract] [Object] To solve the drawbacks of the conventional extruded propylene resin foam using non-crosslinked propylene resin as the base resin, and to provide excellent foaming properties from low expansion ratio to high expansion ratio. Get the body. Also provided is a method capable of easily obtaining a propylene-based resin extruded foam having a wide range of suitable foaming temperatures and excellent properties. The extruded propylene resin foam of the present invention has 2
A non-crosslinked propylene resin having a melt tension at 30 ° C. of 7 gf or more and a half-crystallization time of 800 seconds or more at a crystallization temperature of + 15 ° C., and a density of 0.18
~0.018g / cm ^3, a plate-like extruded foam thickness 10 to 100 mm, was melt-kneaded under high temperature and high pressure in the extruder 1 a base resin, the melt-kneaded product, does not cause foaming The melt-kneaded product is extruded into the accumulator 2 maintained at a temperature and pressure, and then extruded under a lower pressure than in the accumulator 2 and foamed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an extruded propylene resin foam and a method for producing the same.

[0002]

2. Description of the Related Art As a method for producing a long-sized foam or a sheet-like foam for forming a container or the like, a thermoplastic resin is melt-kneaded with a foaming agent in an extruder, and then subjected to low pressure. An extrusion foaming method of extruding and foaming is widely used.

In the extrusion foaming method of an olefin resin, when a melt-kneaded product of a resin and a foaming agent is extruded under a low pressure from an extruder, foaming is performed by expanding the foaming agent in the melt-kneaded material. However, if the temperature of the resin is increased, the viscosity drops sharply, the resin cannot retain the foaming agent, escapes from the resin and becomes a foam of open cells, and conversely, the resin temperature is increased to increase the viscosity of the resin. When the temperature is lowered, the crystallization of the resin proceeds, and as a result, the foam does not foam sufficiently and uniformly, and the foam surface becomes uneven, so that the extrusion foaming is performed with sufficiently uniform foaming and the foaming agent is mixed into the resin. It is necessary to perform viscoelasticity which can be maintained at a temperature of the resin. The temperature range in which viscoelasticity suitable for foaming is obtained differs depending on the type of resin, and this temperature range is generally referred to as a foaming suitable temperature range.

[0004]

However, the propylene-based resin having a higher degree of crystallinity than low-density polyethylene or the like greatly changes the viscoelasticity of the resin due to a slight temperature change, and has a very narrow temperature range for foaming. It is very difficult to carry out extrusion foaming while maintaining the resin temperature within such a narrow temperature range, and when the extrusion foaming temperature fluctuates and deviates from the appropriate foaming temperature range, the foamed portion has an open-cell structure. And the surface became uneven, and it was difficult to obtain a foam having good overall and uniform properties. Conventionally, in the case of a non-crosslinked propylene-based resin, a relatively good foam can be obtained only at a low expansion ratio having a density exceeding 0.2 g / cm ³ or at a density of 0.013 g / cm ^3. It has a high expansion ratio of less than. The above-mentioned problems are considered to be caused by the high crystallinity of the propylene-based resin, and the density is 0.
Extruded foams having a low expansion ratio of more than 2 g / cm ³ can be obtained relatively favorably because the ratio of the resin is larger than the amount of the foaming agent. It is considered that the reason is that the temperature can be set to a considerably higher temperature. The density is 0.013 g / cm ³
The reason why a foam having a high expansion ratio of less than 1 can be obtained relatively favorably is as follows.

In general, a foaming olefin-based resin in the process of extrusion foaming is subjected to a cooling operation from the outside by using a cooling means, whereby the cell walls are solidified to obtain a good foam. However, since the propylene-based resin has a higher degree of crystallinity than low-density polyethylene, the calorific value during crystallization is large. This heat hinders the cooling and thus the solidification of the cell walls, and breaks or deforms the cells of the propylene-based resin in the process of foaming. Therefore, by blending a large amount of a foaming agent and foaming, the temperature of the propylene-based resin in the process of foaming is rapidly lowered by utilizing the heat of vaporization (heat of expansion) of the foaming agent, thereby promoting the solidification of the cell wall. . Further, a large amount of the foaming agent has a function of delaying crystallization of the resin in the extruder. As a result, a relatively good foam can be obtained. However, in this case, the foam obtained necessarily has a density of 0.013 g /
It has a high expansion ratio of less than ³ cm ³ . Also in this case, the suitable foaming temperature range is only about 0.6 ° C.

The present invention has been made in view of the above circumstances,
Density 0.18 to 0.018 g / cm ³ , thickness 10 to 100
It is an object of the present invention to provide a propylene-based resin extruded foam in the form of a plate having a thickness of 1 mm and a method for producing the same.

[0007]

That is, the extruded propylene resin foam of the present invention has a density of 0.18 to 0.018 g / cm ³ and a thickness of 10 based on a non-crosslinked propylene resin.
It is a plate-like extruded foam of about 100 mm, and the melt tension at 230 ° C. of the propylene-based resin as the base resin is 7 gf or more, and the half-crystallization time at the crystallization temperature + 15 ° C. is 800 seconds or more. Features.

Further, the method for producing an extruded propylene resin foam of the present invention has a melt tension at 230 ° C. of 7
gf or more, and a non-crosslinked propylene-based resin having a half-crystallization time of 800 seconds or more at a crystallization temperature of + 15 ° C. and a foaming agent are melt-kneaded in an extruder at high temperature and high pressure. It is extruded into an accumulator maintained at a temperature and pressure at which foaming does not occur. Thereafter, the melt-kneaded product is extruded under a lower pressure than in the accumulator to foam, and has a density of 0.18 to 0.018 g / cm ³ , Thickness 10
It is characterized by obtaining a 100 mm plate-shaped extruded foam.

The melt tension at 230 ° C. used in the present invention is 7 gf or more, and the crystallization temperature is +1.
The non-crosslinked propylene-based resin having a half-crystallization time of 800 seconds or longer at 5 ° C. is a low-temperature decomposition type (decomposition temperature: room temperature to 120 ° C.) C.) and heated to 120 ° C. or lower, and then recombined with a low-molecular-weight polypropylene as a branched chain in the linear propylene-based resin. Is considered to have a branched structure having a long chain branch mainly at the end. As the linear propylene-based resin, propylene homopolymer,
Copolymers of propylene with other olefins and the like can be mentioned. Other olefins copolymerizable with propylene include ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene and the like. Further, as the low-temperature decomposition type peroxide, di (s-butyl) peroxydicarbonate, bis (2-ethoxy) peroxydicarbonate,
Dicyclohexyl peroxydicarbonate, di-n-
Propyl peroxy dicarbonate, di-n-butyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, t-butyl peroxy neodecanoate, t-amyl peroxy neodecanoate and t-
Butyl peroxypivalate is exemplified.

[0010] The non-crosslinked propylene resin used in the present invention is obtained by replacing the linear propylene resin having the isotactic structure with an inert gas such as argon while stirring in a reactor equipped with a stirrer. Then, the above peroxide is usually added in an amount of 5 to 50 mmol per kg of the resin,
While stirring, up to about 120 ° C., preferably 70 to
It is obtained by heating to about 105 ° C. to cause a reaction (usually for 30 to 120 minutes), and then terminating the reaction. When terminating the reaction, a reaction terminator such as methyl mercaptan is introduced into the reaction vessel, or the reaction product is added to
For example, a method of heating to about 150 ° C. for about 20 to 40 minutes is employed.

In the present invention, not only the above resin can be used alone, but also other resins can be mixed with the above resin. As the resin used in combination, for example, a propylene-based resin other than the above, or high-density polyethylene, low-density polyethylene, linear low-density polyethylene,
Ethylene resins such as linear ultra-low density polyethylene, ethylene-butene copolymer, ethylene-maleic anhydride copolymer, butene resins, polyvinyl chloride, vinyl chloride such as vinyl chloride-vinyl acetate copolymer Resins, styrene resins and the like.

In the present invention, the melt tension of the resin can be measured by a melt tension tester. In the present invention, a crystallization rate measuring device can be used for measuring the half-crystallization time. To measure the semi-crystallization rate, first, the support holding the film-like sample is
The sample is completely melted by placing it in an air bath of a crystallization rate measuring instrument. Then, the optical path of the light source and the optical sensor is placed in an oil bath in which the molten sample and the support together with the sample are kept at a temperature of 15 ° C. The voltage of the light source is adjusted so that a constant amount of light is always detected by the optical sensor until the melted sample solidifies again, so as to obtain a voltage-time curve as shown in FIG. Assuming that the voltage when the voltage in this curve becomes a constant value is V ₀ , the voltage is Ｖ V ₀
The time required to reach was defined as the half-crystallization time.

The foam of the present invention has a density of 0.18 to 0.018.
It is a plate-like extruded foam having a g / cm ³ and a thickness of 10 to 100 mm.

In order to obtain the extruded foam of the present invention, as shown in FIG. 2, a resin and a foaming agent are melt-kneaded in a small extruder 1, and the melt-kneaded product in the extruder 1 is extruded. After being extruded and stored in an accumulator 2 having a larger discharge capacity and maintained at a pressure at which foaming does not occur in the melt-kneaded material, a die 3 attached to the tip of the accumulator 2
It is preferable to employ a method of extruding under low pressure to foam and pressing it with the molding device 4 to obtain a plate-like foam having a predetermined thickness. In FIG. 2, 5 is a hopper for supplying raw material resin, 6 is a foaming agent supply pipe, 7 is a piston, 8 is a piston rod, and 9 is a cylinder.

As the foaming agent, an inorganic foaming agent, a volatile foaming agent, a decomposition-type foaming agent and the like can be used. As the inorganic foaming agent, carbon dioxide, air, nitrogen and the like can be used. The volatile blowing agents include propane, n-butane, i
-Butane, pentane, aliphatic hydrocarbons such as hexane, cyclobutane, cycloaliphatic hydrocarbons such as cyclopentane,
Halogenated hydrocarbons such as trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane, methyl chloride, ethyl chloride, and methylene chloride can be used. Further, as the decomposition type foaming agent, azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and the like can be used. These foaming agents can be used by being appropriately mixed. The amount of the foaming agent used depends on the type of the foaming agent, the desired expansion ratio, and the like. For example, the standard of the amount of the foaming agent used to obtain a foam having a density of about 0.2 to 0.013 g / cm ³ is as follows. And about 0.5 to 25 parts by weight (in terms of butane) of a volatile foaming agent per 100 parts by weight of the resin. The amount of the foaming agent used to obtain a foam having a density of more than 0.09 g / cm ³ is estimated based on 100 parts by weight of the resin.
In the case of an inorganic foaming agent, it is about 0.1 to 10 parts by weight, and in the case of a decomposition type foaming agent, it is about 0.1 to 5 parts by weight.

In the present invention, a foam regulator may be further added to the melt-kneaded product of the resin and the foaming agent. Examples of the cell regulator include inorganic powders such as talc and silica, acidic salts of polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate. It is preferable to add about 13 parts by weight or less of the foam control agent per 100 parts by weight of the resin (except when the inorganic filler is contained in a large amount in the resin). Further, if necessary, additives such as a heat stabilizer, an ultraviolet absorber, an antioxidant, and a colorant can be added.

[0017]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. Table 1 shows the physical properties of the resins used in Examples and Comparative Examples. In Examples and Comparative Examples, the amounts of the foaming agent and the foam control agent were such that the sum of these and the resin was 1
It is a weight ratio when it is set to 00 parts by weight. The melt tension of the resin used was measured using a melt tension tester type II manufactured by Toyo Seiki Seisaku-Sho, Ltd. The crystallization speed meter MK- manufactured by Kotaki Shoji Co., Ltd. was used to measure the half-crystallization time.
Type 801 was used.

[0018]

[Table 1]

The measurement of the melt tension is performed as follows. Melt indexer nozzle (caliber 2.0
(95 mm, length: 8 mm) A molten propylene-based resin heated to 230 ° C from above is extruded in a string shape at a constant speed of 10 mm / min under a load from above, and the extruded product is guided to a feed roll through a tension detection pulley. While winding, the winding speed is gradually increased to cut the string, the tension immediately before the cutting is read, and the melt tension (gf) is read.
And However, if the string-like material is not cut at a winding speed of 78.5 m / min, the tension at this time is read and this is defined as the melt tension.

Examples 1-3, Comparative Examples 1-3 Extruders equipped with a single screw of 45 mmφ (L / D ratio =
48) 90mmφ at tip, volume 5 liter, discharge rate 19
An 80 kg / hour accumulator was attached, and the blends in the proportions shown in Table 2 were melt-kneaded in an extruder, and the melt-kneaded product was extruded into an accumulator maintained at a temperature of 160 ° C. and a pressure of 40 kg / cm ^2. After temporarily storing the melt-kneaded material, a plate-like foam was obtained by extruding the melt-kneaded material from a die having a lip gap of 1.5 mm attached to the tip of the accumulator. The state of the obtained foam is shown in Table 2.

[0021]

[Table 2]

The properties of the plate-like foam are as follows: ・ ・ ・: foam having a small surface unevenness, substantially no open cells, and a substantially uniform foam as a whole ×: severe surface unevenness or corrugation, or continuous The foam was evaluated as a foam having a large number of cells and a non-uniform whole. After production, the foams obtained in Examples 1 to 3 were allowed to stand at room temperature for one week, and the density was measured. On the other hand, Comparative Example 1
In the case of ~ 3, the foam shrank significantly during the production.

[0023]

As described above, in the method of the present invention, since the foaming suitable temperature range is wider than in the conventional extrusion foaming method using a non-crosslinked propylene resin as a base material, it is easy to control the extrusion foaming temperature. By using a non-crosslinked propylene-based resin as the base resin, it is possible to produce a thick plate-like extruded foam having excellent properties, which is entirely uniform and free from shrinkage and corrugation.

[Brief description of the drawings]

FIG. 1 is a voltage-time curve obtained by crystallization rate measurement.

FIG. 2 is a schematic view showing an example of an extrusion foaming apparatus.

[Explanation of symbols]

 Reference Signs List 1 extruder 2 accumulator 3 die

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FIB29L 7:00 C08L 23:10 (72) Inventor Takeshi Aoki 690-6 Noguchi, Nikko-shi, Tochigi Prefecture

Claims (2)

[Claims] 1. A non-crosslinked propylene resin-based substrate having a density of 0.18 to 0.018 g / cm ³ and a thickness of 10 to 10
It is a plate-like extruded foam of 0 mm, and the melt tension at 230 ° C. of the propylene resin as the base resin is 7
A propylene-based resin extruded foam having a gf or more and a half-crystallization time of 800 seconds or more at a crystallization temperature of + 15 ° C. 2. Melt tension at 230 ° C. is 7
gf or more, and a non-crosslinked propylene-based resin having a half-crystallization time of 800 seconds or more at a crystallization temperature of + 15 ° C. and a foaming agent are melt-kneaded in an extruder at high temperature and high pressure. It is extruded into an accumulator maintained at a temperature and pressure at which foaming does not occur. Thereafter, the melt-kneaded product is extruded under a lower pressure than in the accumulator to foam, and has a density of 0.18 to 0.018 g / cm ³ , Thickness 10
A method for producing a propylene-based resin extruded foam, characterized in that a 100 mm plate-shaped extruded foam is obtained.