WO2007011045A1

WO2007011045A1 - Purging agent

Info

Publication number: WO2007011045A1
Application number: PCT/JP2006/314539
Authority: WO
Inventors: Naoki Kataoka; Hiroyuki Shindome; Tomoyuki Watanabe
Original assignee: Kuraray Co., Ltd.
Priority date: 2005-07-20
Filing date: 2006-07-18
Publication date: 2007-01-25
Also published as: JPWO2007011045A1

Abstract

Disclosed is a purging agent used for resin molding apparatuses. The purging agent comprises an ethylene-vinyl alcohol copolymer, an alkaline earth metal salt and a boron compound. The purging agent contains 8-80 μmol of the alkaline earth metal salt and 8-80 μmol of the boron compound per 1 g of the ethylene-vinyl alcohol copolymer. The limiting viscosity [η] of the ethylene-vinyl alcohol copolymer contained in this purging agent is not more than 0.120 L/g, and the melt viscosity index MI of the purging agent at 190˚C is not more than 0.70 g/10 min. By using such a purging agent, resin residues remaining in a resin channel in a molding apparatus can be easily removed. In addition, the purging agent can be discharged in a short time when operation of the molding apparatus is resumed.

Description

Purging agent Technical field

The present invention relates to a purging agent used for removing a resin residue existing inside a resin molding apparatus. More specifically, the resin residue generated when melt-molding a resin composition containing a thermoplastic resin or a mixture thereof, in particular, an ethylene-butalcohol copolymer (hereinafter sometimes referred to as EVOH) is used as a device. It relates to a purging agent for removal from the inside. The present invention also relates to a purging method using the purging agent. Background art

E VOH is recognized as a packaging material for food and other packaging films, containers, especially foods that require oxygen barrier properties, and products that require fragrance retention. 'In addition, EVOH has excellent barrier properties against gasoline and is used as a raw material for plastic fuel tanks.

E V OH is formed into various molded products by melt molding, either alone or mixed with other thermoplastic resins. However, when melt molding, for example, melt extrusion molding, is performed using EV OH or a mixture of E VO H and another thermoplastic resin, if a long time operation is performed, the resin flow path of the molding apparatus These resins may stay and gel or decompose, resulting in the formation of foreign substances such as gelled products and bumps. As a result, powder or gel-like materials may be mixed in the resulting product, or streaks may appear in the product, or thickness unevenness may occur in the product, resulting in a poor appearance.

In particular, recycled materials containing EV OH (E VOH and other resin bra This tendency is remarkable when a resin product is manufactured using a resin mixture obtained by recovering scrap resin generated when a stick product is manufactured. For example, a plastic fuel tank generally has a multilayer structure including a recycled material layer (for example, high density polyethylene (HDPE) outer layer / recycled material layer / adhesive layer / EVOH layer Z adhesive layer / HDPE inner layer) There are cases in which the recycled material layer contains gel-like materials, bushes, etc. that are thought to be generated by excessive heating.

Furthermore, when molding is performed using EVOH or a resin mixture containing EVOH and a thermoplastic resin (hereinafter sometimes referred to as EVOH-containing resin composition), if the operation of the device is stopped, In many cases, resin-modified products derived from these resins (such as EVOH yellowed due to deterioration, gelled products derived from EVOH, foamed decomposition products, etc.) remain, or they often occur over time. Therefore, when the operation is resumed, these modified resins are discharged over a long period of time together with the newly introduced molding resin. Therefore, it takes a long time to obtain a normal product, and many non-standard products are generated. In the worst case, it is necessary to disassemble the device and clean the inside of the flow path. In particular, the plastic fuel tank molding and processing apparatus is much larger and more complex than the food packaging molding apparatus, and the disassembly and cleaning of the flow path requires a great deal of cost and time.

In order to solve these problems, if abnormalities such as gels and streaks are found in the molded product during the long-term operation of the molding equipment, or if the operation is stopped, the inside of the resin flow path is filled with a predetermined resin The method of replacing with (the method of purging) is adopted. For example, when melt molding using EVOH-containing thermoplastic resin, resins such as HDPE, linear low-density polyethylene, polystyrene, and polypropylene are used as purging agents. In order to increase the efficiency of purging, a resin having a low melt viscosity index (melt index; sometimes abbreviated as Ml) (for example, 0.05 to 10 101! 1 at 190 ° C) in.) is used as a purging agent, or steps are taken to switch to a low M l resin step by step to lower the extrusion temperature or increase the discharge rate.

However, the purging operation is complicated and takes a long time, and a large amount of purging agent is required. Furthermore, after purging with the resin, when the resin material for molding (for example, the EVOH-containing resin composition) is introduced into the resin flow path and the operation of the molding apparatus is restarted, the purging agent itself Has the disadvantage of being difficult to discharge. In particular, as described above, when a resin having a low Ml is used in order to increase the purging efficiency, there is a drawback in that it is not easily discharged because the fluidity at the time of melting is low. As a result, products containing purging agents are produced over a long period of time. Such products are contaminated with gels or gums resulting from purging agents. Alternatively, when obtaining a stretched product, problems such as tearing of the product due to gels or sticky materials caused by the purging agent, pinholes, and the like. Thus, it takes a long time to obtain a normal product.

As a countermeasure against this, when the EVOH-containing resin composition is introduced into the resin flow path and the operation is restarted, prior to the introduction of this resin composition, a method of gradually increasing the M l of the purging agent (that is, , Using a plurality of purging agents with different M l, putting them into the molding equipment in order from the lower M l, and thereby changing the MI of the purging agent in the resin flow path in a stepwise manner) Some have been adopted. However, there are drawbacks in that the operation is complicated, takes a long time, and requires a large amount of purging agent.

Japanese Patent Application Laid-Open No. 5-27 9 5 18 discloses a purging agent comprising a composition containing a polyolefin resin and a Group II metal salt. This purging agent has a relatively excellent effect. This document describes that the purging agent may contain EVOH as required. However, if it contains E VOH, that is, a mixture of polyolefin and E VOH. In some cases, during purging, these molten resins react and easily gel. For this reason, such a purging agent has poor removal efficiency of gelated substances staying in the resin flow path.

Furthermore, Japanese Patent Application Laid-Open No. 5-26 9 75 4 discloses a purging agent made of a thermoplastic resin having a predetermined MI. It is described that E V OH is suitable as such a resin. Furthermore, it is described that a mixture obtained by adding a predetermined amount of a predetermined metal salt and an acidic substance to this EVOH is used as a purging agent. This document describes that in order to increase the efficiency of purging, it is preferable to use a resin having a low MI at the beginning of melting as a purging agent.

However, resins with low M l have a high degree of polymerization, and such purging agents containing E VO H with a high degree of polymerization have low thermal stability. For this reason, when the operation is resumed, there may be cases where heat-degraded products derived from the purging agent are mixed into the product. Disclosure of the invention

As described above, when the EV OH-containing resin composition is formed by a method such as melt extrusion, if the melt extrusion is performed for a long time or the operation is resumed after the melt extrusion is stopped, the resin gelates, deteriorates or decomposes. Gels, bushes, streaks, etc. resulting from such factors are mixed into the product. Accordingly, an object of the present invention is to provide a purging agent capable of effectively removing a gelled, deteriorated or decomposed resin remaining in a resin flow path of a molding apparatus; and the above EV OH-containing resin composition The object is to provide a purging agent that can be discharged in a short time when the operation of the molding apparatus is resumed using an object.

The purging agent of the present invention contains an ethylene monobutyl alcohol copolymer, an alkaline earth metal salt, and a boron compound, and 1 g of the ethylene monobutyl alcohol copolymer contains the alkali earth metal. Salt is 8-8 0 μ πι ο 1, and The boron compound is contained at a rate of 8 to 80 / zmo 1, and the intrinsic viscosity [η] of the ethylene-vinyl alcohol copolymer is 0.120 L / g or less, and 190% of the purging agent. The melt viscosity index MI at 0 ° C is 0 · 70 g / 10 min or less.

In one embodiment, the alkaline earth metal salt is an alkaline earth metal salt of a fatty acid.

In one embodiment, the boron compound is boric acid.

In the purging method of the present invention, the purging agent is introduced into a resin molding apparatus to bring the resin residue present inside the molding apparatus into contact with the purging agent, and then the resin residue is purged with the purging agent. And removing from the molding apparatus together with the agent.

In one embodiment, the resin residue is derived from a resin composition containing an ethylene-vinyl alcohol copolymer subjected to molding.

BEST MODE FOR CARRYING OUT THE INVENTION

The purging agent of the present invention contains EVOH, alkaline earth metal, and boron compound. The components contained in the purging agent of the present invention, the purging agent, and the purging method using the same are described below.

I. Ethylene-vinyl alcohol copolymer (EVOH)

EVOH used in the purging agent of the present invention is an ethylene monoacetate butyl saponified copolymer. EVOH used in the present invention has an intrinsic viscosity of 0.120 LZg or less. The intrinsic viscosity of EVOH is measured by the method described in Examples below. When the above intrinsic viscosity [77] is higher than 0.120 L / g, the viscosity of the purging agent itself becomes extremely high, and the purging agent is not easily discharged from the resin flow path. Further, the intrinsic viscosity of EVOH is preferably not less than 0.090 LZg. The ethylene content of EV OH is preferably 15 to 70 mol%, more preferably 20 to 60 mol%, and the degree of saponification of the vinyl acetate moiety is preferably 90% or more, Preferably it is 95% or more. This EV OH may be modified with a small amount of copolymerization monomer. Examples of the modifying monomer include propylene, 1-butene, 1-hexene, 4-methyl-11-pentene, acrylic acid ester, methacrylic acid ester, maleic acid, phthalic acid, itaconic acid, alkyl vinyl ether, N-butylpyrrolidone. N-normal butoxymethylacrylamide, N- (2-dimethylaminoethyl) methacrylamides or their quaternized compounds, N-vinylimidazole or its quaternized compounds, and olefinic unsaturated monomers (containing kale) Vinyltrimethoxysilane, butyltrimethoxysilane, butylmethyldimethoxysilane, butyltrimethoxysilane, etc.).

This EVOH is usually saponified by adding caustic alcohol or alkali metal alcoholate to an alcohol solution of ethylene-vinyl acetate copolymer, and then washing sodium acetate, which is a by-product during saponification, with water. Then, it is obtained by adding an acid, immersing it in an acid solution, and adding a combination of a certain metal salt and an acid.

I I. Al force earth metal salt

As the alkaline earth metal salt used in the purging agent of the present invention, an alkali metal salt of fatty acid is preferably used. Examples of the fatty acid include fatty acids having 12 to 30 carbon atoms such as stearic acid and palmitic acid. Al-powered earth metals include magnesium, calcium, and barium. As the alkaline earth metal salt, magnesium stearate, calcium stearate or the like is preferably used, and magnesium stearate is more preferably used. These alkaline earth metal salts may be used alone or in combination of two or more May be used in combination.

Alkaline earth metal salts have a function of acting on the EVOH main chain and cutting it when the purging agent is heated and melted. Therefore, when the purging agent is introduced into the resin flow path of the molding apparatus, it has a function of decomposing the resin residue derived from E V O H present in the flow path. Further, after removing the resin residue, E V O H in the purging agent present in the flow path is decomposed to lower the molecular weight, so that the purging agent can be easily discharged.

The alkaline earth metal salt is contained in an amount of 8 to 80 / mol, preferably 17 to 42 / mol, and more preferably 25 to 40 / z mol per 1 g of EVOH. When the amount of the alkaline earth metal salt is less than 8 / m o 1, the resin residue is not sufficiently decomposed, and as a result, the resin residue may be insufficiently removed. On the other hand, if it exceeds 80 μπιο 1 / g, the purging agent itself decomposes severely and does not exhibit an effective purging effect. I I I. Boron compounds

Examples of the boron compound used in the purging agent of the present study include boric acids, borates, borates, and borohydrides. Specifically, examples of boric acid include boric acid, orthoboric acid, metaboric acid, and tetraboric acid. Examples of boric acid esters include triethyl borate and trimethyl borate. Examples include alkali metal salts of the above various boric acids, alkaline earth metal salts, and borax. Of these compounds, boric acid is preferred. These boron compounds may be used alone or in combination of two or more.

Boron compounds have the function of crosslinking EVOH and lowering its Ml when the purging agent is heated and melted. Therefore, when the purging agent is introduced into the resin flow path of the molding device, the MI of the purging agent decreases, and the adhering resin is removed. It can be effectively removed.

The boron compound is contained in an amount of 8 to 80 μιαο 1, preferably 16 to 70 / mol, and more preferably 20 to 48 μπιο1 with respect to 1 g of EVOH. When the amount of the boron compound is less than 8 μπιο1, when the purging agent is heated and melted and introduced into the resin flow path of the molding apparatus, it is relatively less than the viscosity of the resin residue adhering to the resin flow path. Therefore, the resin residue cannot be removed sufficiently. Conversely, if it exceeds 80 μπιο 1 / g, the viscosity of the purging agent itself becomes extremely high, and the purging agent itself is not easily discharged from the resin flow path.

I V. Purging agent and purging method using the same

As described above, the purging agent of the present invention contains EVOH, alkaline earth metal, and boron compound in the predetermined ratio. Specifically, the purging agent is obtained by mixing these components, and the mixing order is not particularly limited.

The melt viscosity index Ml at 1 90 ° C. of this purging agent is 0.70 g / 10 min or less, preferably 0.60 g / 10 min or less. Accordingly, the types and amounts of the EVOH, the alkaline earth metal, and the boron compound are appropriately set so as to achieve such a melt viscosity index. The melt viscosity index (Ml) of the purging agent is preferably 0.20 gZl Omin or more. When the above MI exceeds 0.70 gZl 0min, the purging performance is insufficient. The melt viscosity index is measured by the method described in Examples below. This purging agent usually has an intrinsic viscosity that is almost the same as the intrinsic viscosity of the contained EVOH. The purging agent of the present invention is particularly useful for removing resin residues present in a molding apparatus when molding is performed using a resin composition containing EVOH. As a resin composition containing EVOH used for the above molding, ethylene-vinyl A resin mixture containing 1 to 50% by mass of a rualcohol copolymer is preferred. Examples thereof include recovered resins such as scraps and burrs generated during the formation of a multilayer structure including an EVOH layer, and EVOH is preferably contained in a proportion of 1 to 50% by mass. Examples of thermoplastic resins other than EVOH include polyolefins (polyethylene, polypropylene, etc.), unsaturated carboxylic acids or their anhydrides, modified polyolefins, polystyrene, polyamides, polyesters, polybutyl chloride, and polyvinylidene chloride. Of these, polyolefin is particularly preferred. These thermoplastic resins may be contained alone or in combination of two or more.

The perzinc agent decomposes EVOH and the gelled product formed by the reaction of EVOH with other resins, lowers the viscosity, and facilitates discharge. Therefore, the EVOH content in the resin composition used for the above molding is 1 mass. If it is less than ₀ , the effect of the purging agent may not be fully exhibited. On the other hand, if the EVOH content in the resin composition used for molding exceeds 50% by mass, depending on the operating conditions of the equipment, for example, at a high temperature of 260 ° C or higher, the EVOH content may be low. Viscosity may progress too much and the purging effect may be reduced. In particular, a resin composition containing EVOH in a proportion of 1 to 40% by mass is suitable.

The action when purging using the purging agent of the present invention is not particularly limited, but for example, the following actions can be considered.

The purging agent of the present invention has a function of decomposing a resin residue such as a gelated product generated by the reaction of EVOH and EVOH with another resin by the action of an alkaline earth metal. As a result, the resin residue in the molding apparatus becomes low in viscosity and can be easily discharged. This decomposition proceeds gradually. On the other hand, at the initial stage of melting, EVOH is cross-linked by the action of the boron compound, so the viscosity of the parsing agent became high (Ml decreased) and the resin residue or decomposed. Resin residue can be easily discharged. After the purging is completed, the decomposition of the purging agent gradually proceeds to lower the viscosity, so that the purging agent itself can be easily discharged. Next, a specific example of the purging method of the present invention will be described. After molding a resin or a resin composition intended for molding, for example, the above EVOH-containing resin composition using a molding apparatus, for example, a melt extrusion apparatus, the purging agent is put into the extrusion apparatus, Purging resin residue that remains (present) in the road. The melt extrusion apparatus is not particularly limited. For example, a single screw extruder, a twin screw extruder, a single layer film forming machine, a single layer inflation film forming machine, a coextrusion sheet film forming machine, a coextrusion film forming machine. And co-extrusion blow molding machine, co-injection molding machine and the like. As for the purging agent, it is desirable to add about 6 to 20 times the amount of the resin remaining in the extruder after the resin composition disappears in the hopper into which the resin composition used for molding is placed. In order to effectively perform purging, it is effective to increase the screw rotation speed, periodically increase or decrease the rotation speed, or change the extrusion temperature (for example, increase the temperature). Furthermore, in order to effectively replace the resin flow path with a purging agent, prior to the introduction of the purging agent, M l is higher than the resin composition used for molding, and MI is lower than the purging agent. When polyolefin is introduced, it is more effectively replaced with a purging agent.

After purging is completed, the operation may be stopped by lowering the temperature, and the operation of the molding apparatus may be resumed immediately using the resin composition. When resuming operation, the temperature is maintained or raised while the purging agent remains in the molding equipment, and the extruder is stopped for about 1 to 48 hours, thereby purging in the extruder. After decomposing the agent to increase its melt index, the resin composition intended for molding can be added to continue the operation. In order to obtain a normal product quickly, a plurality of purging agents with different M l are used, and the purging agents with lower M l are introduced into the molding apparatus in order (in stages). Then, it may be preferable to introduce a resin composition intended for molding. When restarting the operation by raising the temperature after stopping the operation, it is preferable to perform extrusion for a short period of time with a purging agent and then switch to a resin composition intended for molding. In this case as well, it is more effective to change the purging agent to a purging agent having a high melt index in a stepwise manner, and then to switch to a resin yarn and composition for the purpose of molding.

As described above, the purging agent of the present invention can be used to remove a resin remaining in a resin flow path inside the apparatus or a modified product (resin residue) such as a gel derived from the resin in a thermoplastic resin melt molding apparatus. It is possible to remove it quickly. This purging agent is particularly effective when a resin composition containing EVOH is melt-molded, and the purging agent itself can be quickly discharged from the apparatus. Therefore, when the device is operated again after purging, the product loss due to mixing of the purging agent can be greatly improved. Therefore, the purging agent of the present invention and the purging method using the same are advantageously used particularly in the production of various resin molded products containing EVOH, and in the production of various molded products using a recovered resin containing EVOH. The Example

Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto. In the following examples and comparative examples, the intrinsic viscosity of EVO H and the melt viscosity index (melt index; M I) of the purging agent were measured by the following methods.

(I) EVOH intrinsic viscosity

Dry the sample EVOH, weigh exactly 0.2 g of the sample, add it to hydrous phenol (water: phenol (mass ratio) = 15: 85) 4 OmL, and heat to 60 ° C for 4 hours. To dissolve. The resulting liquid (water content of EVOH Measure phenol solution) at 30 ° C using a Ostwald viscometer. Intrinsic viscosity [77] is calculated by the following formula.

Intrinsic viscosity [77] (L / g) = {(2 X (^ sp-ln ^ rel)) ^1/2 } / C

Where C is the EVOH concentration (gZL); and 77 sp and Tj rel are the specific viscosity (specif i C V1SCOS1 ty) and relative viscosity (relative viscosity), respectively. 77 sp and rel are given by:

η sp = t / t 0- 1

77 rel == t / t 0

Here, t o is the time for the blank hydrophenol to pass through the viscometer (90 seconds here), and t is the time for the EVOH hydrophenol solution to pass through the viscometer.

(I I) Melt viscosity index (M I)

Measured according to the condition D (190 ° C, 2160 gf) of the measurement method (Method A) of menoleto mass flow rate described in JISK 72 10 Is calculated.

(Example 1)

(1) Production of purging agent

The purging agent in the present invention was produced by melt extrusion as follows. Ethylene content as the EVOH 3 2 mole ^_0/0, a saponification degree of 9 9.6 mole ^_0/0, and the intrinsic viscosity [77] of 0. 1 1 2 LZg Ebaru F 1 0 1 (Co. Kuraray-made Prepared. EVOH 25 kg, boric acid 50 g (0.2 phr with respect to EVOH mass; 3 2.3 μπιο 1 per EVOH mass), and magnesium stearate 500 g (2 phr with respect to EVOH mass; EVO H Weighed 33.3 / zmol per lg. Next, these raw materials were put into a 120 L tumbler and mixed for 10 minutes. Mixed Using a raw material of 25 mm φ twin screw extruder (two screw same direction screw: L / D 25 segment type, fixed feeder: single screw auger screw, strand die: Φ3 mm, 3 holes), molding temperature 210 ° C, Extrusion was performed under the conditions of a screw speed of 150 rpm and a discharge amount of 4.5 kgZhr, and the strand was forced with a pelletizer while cooling in a cooling water bath to obtain a cylindrical-shaped purging agent pellet. The obtained purging agent pellet had an MI of 0.50 g / min 0 min at 190 ° C.

(2) Evaluation of purging agents

(2.1) Evaluation of deposits in the die

2 温度 ιηιηΦ—shaft extruder (shallow groove screw: LZD = 20, full fray, compression ratio: 4.0, die: straight 300 mm wide die, screen: 50/100/50 mesh), molding temperature 220 ° Operation was performed under the conditions of C, screw rotation speed of 33 rpm, and discharge rate of 1 kgZhr, and EVOH (Eval F101) was extruded for 1 hour. The EVOH in the screw was completely extruded and stopped with EVOH filled in the die. Next, the liplo of the dice was immediately closed with a Teflon sheet and a wooden board. Immediately after that, the temperature of the extruder was immediately raised to 240 ° C and held for 16 hours to prepare a model for EVOH residence deterioration. Next, the temperature of the extruder was lowered to 220 ° C, the lip was opened, and 500 g of recovered resin containing EVOH was introduced into the extruder at 66 rpm (1.4 kg / hr) and filled. Was replaced with this recovered resin. This recovered resin is a resin that contains 7% by mass of EVOH, which is obtained by recovering scrap burrs generated during the formation of plastic fuel tanks. Next, 500 g of low-density polyethylene (MI = 190 g / 10 min in 190 ° C) was introduced into the extruder at 66 rpm (l. 5 kg / hr) and filled, and the interior was filled with this low-density polyethylene. Substituted with density polyethylene. Next, 800 g of the purging agent obtained in the above item (1) was introduced into the extruder at 66 rpm (2.0 kg / hr), and stopped with the resin remaining on the screw rod. Next, the lip opening of the die was immediately closed with a Teflon sheet and a wooden board. Immediately thereafter, the temperature of the extruder was raised to 240 ° C and held for 2 hours. After 2 hours, the extruder temperature was lowered to 220 ° C, the lip was opened, and high-density polyethylene (Ml 0.07 g / 1 Om i n. At 190 ° C) 50 O g, 66 r pm (l 5 kg "hr) was introduced into the extruder, and the above purging agent was discharged. Then, the die was opened, and the deteriorated EVOH adhering to the die surface was collected. The mass of the collected amount in the die was weighed. The evaluation was made according to the following criteria: The results are shown in Table 1.

(Evaluation criteria)

A: Less than 0.5 g

B: 0.5 g or more and less than 1.0 g

C: 1.0 g or more

(2.2) Evaluation of thermal stability of purging agent

2 ΟπιπιΦ—Screw Extruder (Shallow Groove: L / D: 20, Full Flight Compression Ratio: 4 · 0, Die: Straight 300 mm Wide Die, Screen: 50/100/50 Mesh) Purging agent was introduced and operated for 1 hour under conditions of extruder internal temperature 220 ° C, screw rotation speed 33 rpm, and discharge rate lkg no hr. The operation was stopped in the filled state. Next, the Ritz Pro of the dice was immediately closed with a Teflon sheet and a wooden board. Immediately after that, the temperature of the extruder was immediately raised to 240 ° C and held for 2 hours to create a residence degradation model for the purging agent in the extruder. Next, the temperature of the extruder is lowered to 220 ° C, the lip is opened, and the Epal F 101 is extruded under the conditions of 33 r pm and a discharge amount of 1 k gZhr, and cooled on a cooling roll at 80 ° C. A film with a thickness of 20 μπι I got Lum. After 30 minutes, the number of butches having a diameter of 8 μμπι or more present in the obtained Finolem 10 cm × 10 cm (100 cm ² ) was counted, and the film surface state was evaluated according to the following criteria. The results are shown in Table 1.

(Evaluation criteria)

Film surface rank A: Number of books is less than 5

Film surface rank B: Number of books 5 or more and less than 20

Film surface rank C: 20 or more

(Example 2)

As shown in Table 1, except that the amount of boric acid was changed, purging agent pellets were obtained in the same procedure as in Example 1, and evaluation was performed using this. The results are shown in Table 1. The results of Example 3 and Comparative Examples 1 to 3 below are also shown in Table 1.

(Example 3)

As shown in Table 1, except for changing the amount of magnesium stearate, a purging agent pellet was obtained in the same procedure as in Example 1 and evaluated using this.

(Comparative Example 1)

As shown in Table 1, a purging agent pellet was obtained in the same manner as in Example 1 except that the amount of boric acid was changed, and evaluation was performed using this.

(Comparative Example 2)

In this comparative example, an ethylene content of 29 mol% as EVOH, the saponification degree of 99.6 mole ^_0/0, and the intrinsic viscosity [7]] was used EVOH of 0. 125L // g. Use this EVOH, without adding boric acid, acetic acid EVOH mass In the same procedure as in Example 1 except that potassium dihydrogen phosphate was added so as to be 0.02 phr with respect to EV OH mass, and l OO p pm. I got a pellet. Evaluation was performed in the same manner as in Example 1 using this pellet. This purging agent corresponds to the purging agent described in Example 2 of JP-A-5-269754.

(Comparative Example 3)

Except that the amount of magnesium stearate was changed as shown in Table 1, purging agent pellets were obtained in the same procedure as in Example 1, and evaluation was performed using this.

table 1

* 1: EVOH MI at 190 ° C

As shown in Table 1, it can be seen that when the purging agent of each example is used, purging of the extruder resin flow path is effectively performed, and the thermal stability of the purging agent is sufficient. In comparison with this, in each of the comparative examples, both the purging effect and / or the thermal stability were insufficient. In the purging agent of Comparative Example ² , the intrinsic viscosity of EV OH is higher than that in Example 1, so that it was expected from the conventional knowledge that purging efficiency was improved. However, compared with the purging agent obtained in Example 1, the thermal stability was clearly inferior. Industrial applicability

According to the present invention, in a thermoplastic resin melt molding apparatus, a purging agent capable of quickly sweeping away a resin remaining in a resin flow path inside the apparatus or a modified material such as a gel derived from the resin is provided. The This purging agent is especially E VO This is effective when melt-molding a resin composition containing H, and the purging agent itself can be quickly discharged from the apparatus. For this reason, when the apparatus is operated again after purging, the product loss due to mixing of the purging agent can be greatly improved. Therefore, the purging method using the purging agent of the present invention is particularly suitable for the production of various resin molded articles containing EV OH, or for various molded articles containing a recovered resin containing EV OH. It is advantageously used for manufacturing.

Claims

The scope of the claims

1. a purging agent,

Containing an ethylene-vinyl alcohol copolymer, an alkaline earth metal salt, and a boron compound,

The alkaline earth metal salt is contained in an amount of 8 to 80 μπιο 1 and the fluorine compound in an amount of 8 to 80 μm o 1 per 1 g of the ethylene monobutyl alcohol copolymer,

The intrinsic viscosity of the ethylene-vinyl alcohol copolymer [rj] force SO. 120 L / g or less, and

A purging agent having a melt viscosity index M I at 190 ° C of not more than 0.70 gZlO m i n.

2. The purging agent according to claim 1, wherein the alkaline earth metal salt is an alkaline earth metal salt of a fatty acid.

3. The purging agent according to claim 1, wherein the boron compound is boric acid.

4. By introducing the purging agent according to any one of claims 1 to 3 into a resin molding device, the resin residue present in the molding device and the purging agent are brought into contact with each other, and then the resin residue A method for purging a thermoplastic resin, comprising a step of removing an object together with the purging agent from the molding apparatus.

5. The purging method according to claim 4, wherein the resin residue is derived from a resin composition containing an ethylene monobutyl alcohol copolymer subjected to molding.