JPH07179645A - Foamed particle comprising polyamide resin - Google Patents

Abstract

PURPOSE:To obtain a foamed particles desirable as an artificial soil excellent in heat resistance, chemical resistance, especially water retentivity, lightweight properties and a capability of dispersing air bubbles by extruding a polyamide resin having a specified water content into a strand and cutting this strand into particles. CONSTITUTION:The surface temperature of a pelletized polyamide resin prepared by the ring opening polymerization of a lactam or the polycondensation or the like of a lactam with an amidocarboxylic acid and having a water content of 0.1-50wt.% is kept at 50-150 deg.C; steam adjusted by the amount of steam of a mixed gas is blown against the surface; the entire is stirred with a blender, a mixer or the like; 1-5 pts.wt., per 100 pts.wt. water-containing polyamide resin, organic or inorganic volatile blowing agent is optionally blended directly or in the form of a premix with the resin with the mixture; the resulting mixture is melt-kneaded at 220-270 deg.C with an extruder fitted with a strand die to form a strand-like foam having a diameter of 1-3mmphi; and this foam is cut with e.g. a pelletizer to obtain cylindrical foamed particles of a length of 2-3mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a polyamide-based expanded granular material comprising a polyamide-based resin suitable for artificial soil. Specifically, a polyamide-based resin containing a specific amount of water has fine pores, for example, is melt extruded and foamed into a fine shape from a strand die, and then the expanded fine material (for example, a string) is granulated. The present invention relates to the provision of a polyamide-based foamed granular material which is excellent in water retention and lightness after being cut and which is suitable for, for example, artificial soil.

[0002]

2. Description of the Related Art Conventionally, for example, as artificial soil,
Expanded granules made of a plastic resin, for example, foamed granules obtained by mixing an organic foaming agent, an inorganic foaming agent, etc. with a polyolefin resin such as polyethylene resin, polypropylene resin, etc. and melt-extruding and foaming, and further low volatility. Foamed granules and the like are used in which a volatile gas or the like is blown into a molten resin and melted and extruded to foam.

[0003]

However, since the polyolefin resins such as the polyethylene resins and polypropylene resins described above have high crystallinity, the melt viscosity rapidly decreases when heated above the melting point, It tends to be difficult to sufficiently contain the added foaming agent gas, low volatility gas, etc. in the resin, and fine bubbles (cells) are uniformly dispersed, and the foam has excellent water retention, lightweight properties, etc. Obtaining granules tended to be very difficult.

For this reason, the expanded granules made of a polyolefin resin such as a polyethylene resin and a polypropylene resin are produced from a resin cross-linked by electron beam irradiation, addition of an organic oxide, etc., but the foamability is poor. , Water retention,
The weight was poor and the moldability was insufficient.

In order to solve the above problems, the present inventor has
As a result of intensive studies on various resins and compositions, it has excellent heat resistance, chemical resistance, light weight, buffering property, flexibility, water retention, etc., and also has extremely fine air bubbles (cells) due to extrusion foaming. It has been found that it is possible to provide a foamed granular material composed of a polyamide-based resin, which is excellent in water retention and lightness and is suitable for artificial soil.

[0006]

A characteristic feature of the present invention is that a polyamide resin containing water is melt-extruded and foamed in a fine shape from a die having pores to form a foamed fine material. Then, in the polyamide-based expanded granules obtained by cutting the fine material into granules, there are provided expanded granules of the polyamide-based resin in which the water content of the polyamide-based resin is 0.1 to 50% by weight. In addition, another point is to provide a foamed granular material made of a polyamide resin obtained by adding a foaming agent to a polyamide resin containing water.

As the polyamide resin according to the present invention,
Although not particularly limited, examples thereof include ring-opening polymerization of lactam, polycondensation of amidocarboxylic acid, polycondensation of diamine and organic dibasic acid, and other polyamide resins.

Specifically, nylon 6, nylon 66,
In addition to nylon 610, nylon 11, nylon 12, etc., nylon 6-66 copolymer, nylon 6-610 copolymer, nylon 6-12 copolymer, etc., or amorphous nylon, polyhexa Examples thereof include aromatic polyamide polymers such as methylene terephthalamide, polyhexamethylene isophthalamide, and pomethaxylylene adipamide, and mixtures thereof. In addition, a polyamide resin capable of forming a thermoplastic film is also included in the scope of the polyamide resin of the present invention. Further, it may be a powder or small pieces obtained by crushing a waste such as a film (including a composite film and a laminated film) made of the above polyamide-based resin or a molded product, or a recycled pellet obtained by granulating these.

When the water content of the polyamide resin according to the present invention is less than 0.1% by weight, the melt viscosity tends to increase when the polyamide resin is melted. Therefore, at the gas pressure of water vapor contained in the polyamide-based resin, a thin material made of the polyamide-based resin (for example,
(Strings, filaments, rods, etc.) tend not to foam, it is difficult to uniformly disperse extremely fine bubbles, and water retention and lightweight tend to decrease, which is not preferred, but it can be used depending on the application. In some cases.

The water content of the polyamide resin is 5
If it exceeds 0% by weight, when the polyamide resin is melted, the melt viscosity of the polyamide resin tends to be significantly reduced. Therefore, the bubbles made of water vapor contained in the polyamide resin are not uniformly included in the molten polyamide-based resin, and the thin objects made of the polyamide-based resin (for example, a string)
Etc. are partially foamed and are likely to tear or break, which is not preferable for artificial soil, for example. These may also be used depending on the application.

As the polyamide-based resin containing water according to the present invention, for example, a pellet-shaped (powder or flake-shaped) polyamide-based resin having a surface temperature of 50 to 50 is used.
Hold at 150 ° C. Next, after spraying water vapor on the surface of the polyamide resin, it is mixed with a known blender, mixer or the like, for example, a ribbon blender, a Henschel mixer or the like, and the water vapor is uniformly adhered to the surface of the polyamide resin. However, there is no particular limitation.

At this time, the surface temperature of the polyamide resin is 5
If the temperature is lower than 0 ° C, the water tends not to be absorbed inside the polyamide resin and foaming does not occur. If the temperature exceeds 150 ° C, the amount of absorbed water increases and the cells (cells) tend to become large, and extremely fine bubbles become uniform. It is not preferable because fine particles (for example, strings) that are not dispersed, and are melted and extruded and foamed are likely to be cut, and it is difficult to obtain foamed granules, which is not particularly limited.

The amount of water vapor sprayed onto the surface of the polyamide resin is not particularly limited, and it is desirable to adjust the amount of water vapor in the mixed gas, for example. The water vapor content in the polyamide-based resin may be adjusted by, for example, the Karl Fischer method or the like and is not particularly limited.

Polyamide resin containing water is
In addition to spraying steam onto the surface of the polyamide-based resin, the polyamide-based resin and water may be directly mixed and heated to absorb the water in the polyamide-based resin, and there is no particular limitation. At this time, the temperature of the mixture of the polyamide-based resin and water is not particularly limited and is preferably in the same temperature range as in the case of the steam spraying.

If necessary, the water-containing polyamide resin according to the present invention may further contain organic, inorganic and volatile foaming agents, and there is no particular limitation.

The foaming agent is not particularly limited, and any known foaming agent may be used. Examples of the foaming agent that can be used include volatile ones such as pentane and butane, and organic ones such as hydrazine and the like. Examples thereof include nitrile-based and azo-based azodicarbonamide, azobisisobutyronitrile, and the like, and inorganic-based materials include sodium bicarbonate, ammonium carbonate, and the like.

The amount of the foaming agent used is not particularly limited, and may be added at least to the extent that the effect is exhibited, but 1 to 5 parts by weight relative to 100 parts by weight of the polyamide resin having a water content of 0.1 to 50% by weight. The part can be illustrated.

The above-mentioned foaming agent may be directly blended with the water-containing polyamide resin according to the present invention, or may be blended by adding a master pellet containing a high concentration of the foaming agent, or may be previously foamed in the polyamide resin. The agent may be appropriately kneaded and used, and the method of adding the foaming agent is not particularly limited.

The polyamide resin containing water thus obtained is melt-kneaded in an extruder equipped with a strand die heated to 220 to 270 ° C., and melt-extruded into fine foam. For example, by being cooled in water kept at, for example, 40 ° C. or less, it was formed into a cord-like foam having a particle size of about 1 to 3 mmφ. Then, a cylindrical foamed granular material having a length of about 2 to 3 mm, which is obtained by sending the string-shaped foamed product to an appropriate pelletizer or the like and cutting it, can be exemplified, but is not particularly limited.

The expanded granular material of the present invention may be manufactured by a method other than the above-mentioned strand method and is not particularly limited. Other than the strand method, there is no particular limitation, for example,
A polyamide resin containing water is extruded into a flat shape or a tubular shape using a T-die, an annular die or the like and foamed to form a foamed film. Then, the obtained foamed film may be cut into a constant width with a slitter, a horizontal cutter or the like to form foamed granules, or the foamed film obtained above may be crushed with, for example, a turbo cutter, etc. The thing etc. can be illustrated.

Further, in the water-containing polyamide resin according to the present invention, if necessary, various additives and fillers such as stabilizers, antistatic agents, lubricants, nucleating agents, flame retardants, Additives such as pigments or dyes, calcium carbonate, silica, talc, fertilizers, etc. can be added and are not particularly limited. Further, the polyamide resin may be blended with other thermoplastic resin and the like, and there is no particular limitation.

The expanded granules made of the polyamide resin of the present invention can be used in various fields due to their excellent properties. For example, it is used as an artificial soil that takes advantage of excellent water retention and lightweight properties, a building material that takes advantage of high strength, a cushioning packaging material that requires cushioning properties, and the like.

[0023]

According to the present invention, when a polyamide resin containing a specific amount of water is melted and extruded, the water vaporizes to become water vapor. This water vapor is contained in the melted polyamide resin, and extremely fine air bubbles are uniformly dispersed, so that it is possible to obtain a foamed granule excellent in water retention and lightweight.

The present invention will be described below based on examples.

[0025]

【Example】

Example 1 Pellets made of nylon 6 were placed in a ribbon blender and heated while rotating the blender to bring the surface temperature of the pellets made of nylon 6 to about 60 ° C. Then
A mixed gas of water vapor and air was blown onto the surface of the pellet to obtain nylon 6 having a water content of 1.0% by weight.

The pellets made of nylon 6 having a water content of 1.0% by weight were melt-extruded and foamed in water whose water temperature was adjusted to 30 ° C. using a strand die at 230 ° C. to give water having a diameter of 2 mm. A string-like foamed fine material made of the contained nylon 6 was obtained. Next, the cord-shaped foamed fine material was sent to a pelletizer and cut into a cylindrical foamed granular material having a size of 2φ × 3 mm.

The foamed granules obtained were such that extremely fine cells (cells) were uniformly dispersed, and the original excellent characteristics of the polyamide resin were not excluded. Table 1 shows the water retention and lightness of the expanded granules. At this time, the water retention is the amount of increase in the weight after soaking a predetermined amount (300 cc) of the foamed granular material in water for 30 minutes, and the lightness is indicated by the apparent specific gravity.

Example 2 Nylon 6 having a water content of 1.0% by weight and the resin 100
1. A blowing agent (azodicarbonamide) is added to 2 parts by weight.
Expanded granules of nylon 6 were obtained in the same manner as in Example 1 except that 0 part by weight was added. Table 1 shows the water retention properties and light weight properties of the expanded granules.

Example 3 As Example 1 except that nylon 6-66 copolymer having a water content of 1.0% by weight was used instead of nylon 6 having a water content of 1.0% by weight. In the same manner, expanded granules made of a nylon 6-66 copolymer having a water content of 1.0% by weight were obtained. Table 1 shows the water retention and lightness of the foamed granular material.
Shown in.

Comparative Example 1 A foamed granular material made of nylon 6 was obtained in the same manner as in Example 1 except that the water content of nylon 6 was 0.05% by weight. The film was one in which fine bubbles were not uniformly dispersed. Water retention of the obtained expanded granules,
The lightness is shown in Table 1.

Comparative Example 2 A foamed granular material made of nylon 6 was obtained in the same manner as in Example 1 except that the water content of nylon 6 was 60% by weight. The granules were not finely sized, were not uniformly dispersed, and were partially foamed. Table 1 shows the water retention property and the lightness of the obtained expanded granules.

Comparative Example 3 Nylon 6 (water content 200 P
A foamed granular material made of nylon 6 was obtained in the same manner as in Example 1 except that 2.0 parts by weight of the foaming agent (azodicarbonamide) was added to 100 parts by weight of PM). Table 1 shows the water retention property and the lightness of the obtained expanded granules.

[0034]

[Table 1]

As is clear from Table 1, the water retention capacity of the comparative examples in which the water content of the polyamide resin is out of the specific amount range (0.1 to 50% by weight) is the water retention capacity of Examples 1, 2 and 3. It is about 50% of the above, and may not be used as, for example, artificial soil. Further, since the apparent specific gravity of Comparative Example is larger than the apparent specific gravity of Example, for example, as artificial soil, foamed granules of Comparative Examples 1, 2, and 3 are obtained. The flowerpot using the body was heavier than the flowerpot using the expanded granular material of the example and was not easy to carry.

[0036]

The expanded granules of the polyamide resin of the present invention are produced by allowing the polyamide resin to contain a specific amount of water, and have extremely fine bubbles uniformly dispersed therein. Moreover, it is possible to provide a polyamide-based expanded granule made of a polyamide-based resin that is excellent in heat resistance, chemical resistance, heat insulation, buffering properties, flexibility, water retention and light weight, etc. .

The expanded granules made of the polyamide resin of the present invention have excellent water retention properties and are therefore suitable as, for example, artificial soil. Moreover, since it is a foam made of polyamide resin, it is lightweight. Therefore, when it is used as an artificial soil such as a flower pot, it is convenient to carry and suitable for cultivating a plant on the roof of a building, for example.

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Claims (2)

[Claims] 1. A polyamide-based resin containing water is melt-extruded and foamed in a fine shape from a die having pores to form a foamed fine article, and then the foamed fine article is cut into granules. The expanded granules, wherein the polyamide resin has a water content of 0.1 to 50% by weight. 2. A foamed granular material made of a polyamide resin according to claim 1, which is obtained by adding a foaming agent to a polyamide resin having a water content of 0.1 to 50% by weight.