JP3179253B2 - Purge agent and purge method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a purging agent for an ethylene / unsaturated carboxylic acid copolymer resin in an extrusion molding apparatus. More specifically, in the extrusion molding of the copolymer resin and the polyolefin resin, when a molding apparatus is shared, the resin is removed from the molding apparatus after molding the copolymer resin, and the normal polyolefin resin is removed. The present invention relates to a purging agent capable of molding in a short time as possible and a purging method using the purging agent.

[0002]

2. Description of the Related Art Ethylene / unsaturated carboxylic acid copolymer,
Ethylene / unsaturated carboxylic acid copolymer resins represented by ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymers or their ionomers are used for forming single-layer or multi-layer films and sheets or lamination molding. It is widely used for molding using an extrusion molding device. Such an extrusion molding device is often used in common with the molding of polyolefin-based resins, particularly polyethylene, and in switching the molding, the resin in the extrusion molding device is sufficiently replaced with a resin that is newly molded, Unless contamination by the previous resin is prevented, regular molding cannot be started. In general, when an ethylene / unsaturated carboxylic acid copolymer resin is fed to an extrusion molding apparatus after the molding of the polyolefin resin, the polyolefin resin in the apparatus is discharged and removed in a relatively short time. A regular molded product of the polymer resin can be obtained in a short time.
However, the reverse case is disadvantageous in that it takes a long time to obtain a desired polyolefin-based resin molded product because the copolymer-based resin has a high adhesiveness to a metal or cannot be easily completely removed. was there.

[0003]

In order to remedy such drawbacks, Japanese Patent Application Laid-Open No. 61-32224 discloses an ethylene / unsaturated carboxylic acid ester resin after extrusion molding of an ethylene / unsaturated carboxylic acid copolymer resin. A method has been proposed in which a polymer is supplied to an extrusion molding apparatus as a purging agent for the resin to drive out the resin, and thereafter, the molding of a polyolefin resin is started, with some success. However, even with this proposal, switching of molding cannot be performed in a sufficiently short time, and further improvement has been desired.

The inventor of the present invention has intensively studied to find a more effective purging agent and a more efficient purging method in order to further improve the productivity. As a result, they found a method of blending an inorganic filler and a chemical foaming agent, more preferably a slip agent, with the ethylene / unsaturated carboxylic acid ester copolymer, and proposed a purge agent blended with these and a purge method using the same. (Japanese Patent Application No. 4-16206)
No. 3). According to this proposal, a remarkable improvement effect was recognized, but the drawback was that the ethylene / unsaturated carboxylic acid ester copolymer as the base polymer was more expensive than polyethylene and the like, and the odor at the time of purging was rather strong. Yes,
We examined for the improvement. As a result, when a blend of polyethylene having a specific melt viscosity and an ethylene / unsaturated carboxylic acid ester copolymer is used as a base polymer, a purging effect comparable to that of the prior application can be obtained, and the above disadvantage can be improved. The present invention has been reached.

[0005]

According to the present invention, polyethylene having a melt flow rate of 0.5 to 5 g / 10 minutes at 190 ° C. and a load of 2160 g, an ethylene / unsaturated carboxylic acid ester, and an inorganic filler are provided. , A purging agent for an extruder comprising a chemical foaming agent and a slip agent, and a purging method using the same.

The ethylene / unsaturated carboxylic acid copolymer resin for extrusion molding to which the purging agent of the present invention is applied is at least one polymer unit selected from unsaturated carboxylic acids, anhydrides and salts thereof, and ethylene polymer units. Is an essential component, and if necessary, a copolymer containing another polymerized unit, for example, an unsaturated ester polymerized unit. More specifically, acrylic acid, methacrylic acid, maleic acid, fumaric acid, monomethyl maleate, unsaturated carboxylic acids such as maleic anhydride or anhydrides thereof, or lithium, sodium, potassium, calcium, magnesium thereof, Polymerized units such as salts of metals such as zinc can be exemplified. In general, those containing a large amount of these polymerized units are difficult to purge from an extruder. Therefore, it is effective to apply the present invention. For example, ethylene is contained in an amount of 20 to 99.9% by weight, particularly 50 to 99% by weight. %, Polymerized units selected from the group consisting of unsaturated carboxylic acids, anhydrides thereof, and salts thereof.
It can be applied to those having a composition of from 40 to 40% by weight, especially from 1 to 35% by weight, and other polymerized units from 0 to 40% by weight, especially from 0 to 30% by weight. Extrusion molding usually has a melt flow rate in the range of about 0.5 to 100 g / 10 minutes at 190 ° C. and a load of 2160 g, and the present invention can be applied to all of these.

The polyolefin resin molded by the same molding machine as the above resin includes medium / high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1 -Pentene, ethylene / vinyl acetate copolymer and the like.

In the present invention, a resin composition containing polyethylene and an ethylene / unsaturated carboxylic acid ester copolymer as a base polymer is used as a purging agent for the ethylene / unsaturated carboxylic acid copolymer resin in an extruder. Can be

The main component of the base polymer of the purge agent of the present invention is polyethylene having a melt flow rate of 0.5 to 5 g / 10 min, preferably 0.5 to 2.0 g / 10 min. Polyethylene melt flow rate is 0.5g / 1
If less than 0 minute is used, the ethylene / unsaturated carboxylic acid copolymer-based resin can be purged from the extruder in a short time, but the purge agent itself is not easily removed from the extruder. This requires a long purge time, which is not preferable. Use of polyethylene having a melt flow rate of more than 5 g / 10 minutes is not preferable because it takes a long time to purge the ethylene / unsaturated carboxylic acid copolymer resin. Polyethylene may be of any production method and density. For example, high-pressure polyethylene, linear low-density polyethylene, medium-high-density polyethylene and the like can be used, and the use of high-pressure polyethylene is particularly preferred.

The other component of the purge agent base polymer of the present invention is an ethylene / unsaturated carboxylic acid ester copolymer. As the unsaturated carboxylic acid ester polymerization unit in the ethylene / unsaturated carboxylic acid ester copolymer, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, Polymerized units such as methyl methacrylate, dimethyl fumarate and diethyl maleate can be exemplified. The copolymer generally contains 70 to 98% by weight of ethylene, preferably 7 to 98% by weight.
5 to 95% by weight, 2 to 30% of unsaturated carboxylic acid ester
It is preferable to select a polymer having a polymerization ratio of 5% by weight, particularly 5 to 25% by weight.
Generally 0.1 to 30 g / 10 min, especially 0.1 to 10 g
g / 10 min.

The use of polyethylene alone requires a long time for purging, while the addition of a large amount of an ethylene / unsaturated carboxylic acid ester copolymer makes it difficult to achieve the above-mentioned object of the present invention sufficiently. , Generally 60 to 99 parts by weight of polyethylene, preferably 70 to 90 parts by weight.
It is preferable to use the copolymer in an amount of 40 to 1 part by weight, preferably 30 to 10 parts by weight (100 parts by weight in total) based on parts by weight.

The purge agent of the present invention contains an inorganic filler, a chemical foaming agent and a slip agent in addition to the base polymer component.

Examples of the inorganic filler powder include silica, talc, calcium carbonate, titanium oxide, alumina, magnesium carbonate, barium sulfate and the like.
For example, those having an average particle diameter of about 0.1 to 10 μm are preferably used. The inorganic filler powder is effective in accelerating the purging, and its addition amount can be widely varied. However, considering the purging effect and the extrusion characteristics, etc., 3 to 100 parts by weight, preferably 5 to 100 parts by weight, per 100 parts by weight of the base polymer component is used. It is desirable to use in a proportion of up to 30 parts by weight.

The purging agent of the present invention also contains a chemical blowing agent which decomposes at the purge temperature to generate gaseous substances. More specifically, azodicarbonamide, dinitrosopentamethylenetetramine, sodium bicarbonate, 4,
4'-oxybisbenzenesulfonyl hydrazide, paratoluenesulfonyl hydrazide, azobisisobutyronitrile, and the like can be used. The use of a chemical foaming agent is useful for accelerating the purging. However, if it is used in an excessively large amount, stable extrusion cannot be performed, and smoke and odor at the time of purging cannot be ignored. It is preferred to use 0.03 to 30 parts by weight, particularly 0.05 to 5 parts by weight per part.

A better purging effect can be expected by adding a small amount of a slip agent to the purge agent of the present invention in addition to the inorganic filler and the chemical foaming agent. As a suitable slip agent, use of a fatty acid amide is preferable, and examples thereof include palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, oleyl palmitamide, stearyl erucamide and the like. Can be. The slip agent should not be used in a large amount, and is preferably used in an amount of 5 parts by weight or less, particularly 0.05 to 3 parts by weight, based on 100 parts by weight of the base polymer component.

The purge agent of the present invention may optionally contain other additives such as an antioxidant and a heat stabilizer.

The purging method using the purging agent of the present invention is preferably performed by the following method. In general, extrusion molding of an ethylene / unsaturated carboxylic acid copolymer resin is performed at an extrusion temperature of, for example, 180 to 330 ° C. When the extrusion is completed, a purge agent is supplied to purge the resin in the extrusion apparatus. Purging with the purging agent of the present invention is performed at an extrusion temperature of 250 to 350 ° C., particularly 3
It can be effectively performed by extruding in the range of 00 to 340 ° C. That is, if the extrusion is performed at a temperature lower than the above-mentioned temperature, a long time is required for purging. On the other hand, if the extrusion temperature is too high, smoke and odor become intense, which is not preferable, and it is necessary to lower the temperature in the next molding of the polyolefin resin. If the molding temperature of the ethylene / unsaturated carboxylic acid copolymer resin is lower than the extrusion temperature of the purge agent, it is necessary to raise the temperature of the extruder.

When purging is performed after the temperature is raised,
After molding the ethylene / unsaturated carboxylic acid copolymer resin,
Although the purge agent of the present invention may be supplied immediately, in order to reduce costs, an inexpensive resin such as low-density polyethylene is supplied during the temperature rise of the extruder, and the purge agent of the present invention is supplied after the temperature rise. May be adopted. Of course, such a method of preliminarily supplying another resin to reduce the use of the purge agent of the present invention can be employed even when the temperature of the extruder is not increased. In any case, by passing the purging agent of the present invention through the extruder at a predetermined temperature, the ethylene / unsaturated carboxylic acid copolymer-based resin in the extruder is purged in a short time. What is necessary is just to start supply of a polyolefin resin. In practice,
It is better to use a method in which the purge agent is supplied for a short time, for example, several minutes, and the supply of the polyolefin-based resin is started at a stage where a small amount of the ethylene / unsaturated carboxylic acid copolymer-based resin still remains in the extruder. It is preferable because the use of an expensive purge agent is minimized and a desired polyolefin resin molded article can be obtained in a short time.

In order to discharge the purge agent together with the remaining ethylene / unsaturated carboxylic acid copolymer resin as soon as possible, a polyolefin resin having a slightly lower MFR than a normal extrusion grade polyolefin resin is used.
After that, it is effective to supply an extruded grade. In order to carry out such an operation efficiently, it is preferable that the purge temperature and the molding temperature of the polyolefin resin are made to coincide.

[0020]

【Example】

[Example 1] A test was performed in the following procedure using an extruder having a diameter of 65 mm L / D = 28 equipped with a screw having a mixing section (compression ratio of 4.8) and an inner deckle die having a width of 850 mm. Methacrylic acid content 9% by weight, melt flow rate (MFR) 8 g / 10 min.
25 kg of blue colored pellets of methacrylic acid copolymer
Extruded at 95 ° C. and 100 rpm. Next, the extruder temperature was set to 320 ° C. and the temperature was increased,
MFR 3.7g / 10min Low density polyethylene 10kg
Was extruded at 50 rpm. Next, 6 kg of a purge agent composition having the composition shown in Table 1 was started, and high-speed purging was performed under the condition of 200 rpm (corresponding to an amount that can be extruded in 4 minutes in terms of calculation). 25 kg density polyethylene, then 3.7 g / 10 MFR
Minutes of low density polyethylene required. After the supply of the purge agent, the molten resin discharged from the die was sampled at regular intervals, the decoloring state and the gel generation state were observed, and the purge effect was evaluated by observing the removal and discharge state of the residual resin. The coloring and gel based on the residual resin of the ethylene / unsaturated carboxylic acid copolymer disappeared in a short time by using the purge agent, there was no strong resin odor, and the switch to polyolefin resin extrusion molding was performed smoothly. . Table 1 shows the results.

For the purpose of observing the decoloration state, the molten resin was collected on a white release paper, and for the purpose of observing the gel, a sagging film was collected. The decoloring status and gel disappearing status are as follows.
It was evaluated on a scale.

Decoloring status Blue residue on the entire surface Blue residue on the die end 10 to 20 cm 〃 5 to 10 cm 〃 以下 5 cm or less 〃 消失 Blue disappearance

Gel disappearance status Multiple occurrences occurred at the entire die end 10 to 20 cm ５〜 5 to 10 cm 〃 以下 5 cm or less 〃 消失 Disappearance

Comparative Examples 1 to 7 In the Examples, ethylene-methacrylic acid copolymers were prepared in the same manner as in the Examples except that various homopolymers shown in Table 1 were used as a purge agent as they were, or as additives. After purging the polymer, the supply was switched to the supply of low-density polyethylene, and the purging effect was measured in the same manner as in the example, based on the decoloring state and the gel generation state. The results are shown in Table 1.

[0025]

[Table 1]

[0026]

By using the purging agent and the purging method of the present invention, it is possible to extrude a polyolefin resin within a short time after extrusion of an ethylene / unsaturated carboxylic acid copolymer resin. it can.

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI // B29K 23:00 (56) References JP-A-2-206635 (JP, A) JP-A-4-183798 (JP, A) JP JP-A-4-183799 (JP, A) JP-A-4-187410 (JP, A) JP-A-61-35224 (JP, A) JP-A-3-230922 (JP, A) JP-A-4-138221 (JP , A) JP-A-4-162603 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 47/00-47/96

Claims (2)

(57) [Claims] 1. A polyethylene having a melt flow rate of 0.5 to 5 g / 10 minutes at 190 ° C. and a load of 2160 g, and an ethylene / unsaturated carboxylic acid ester copolymer;
A purging agent for an extruder comprising an inorganic filler, a chemical foaming agent, and a slip agent. 2. The purging method according to claim 1, wherein the polyolefin resin is molded using the same extruder after extrusion molding of the ethylene / unsaturated carboxylic acid copolymer resin. A purging method characterized by purging an ethylene / unsaturated carboxylic acid copolymer resin staying in a molding machine by supplying an agent and melt-extruding the same.