JP4164653B2 - Method for producing polyamide resin composition and resin molded body - Google Patents

Description

【００３９】
【表２】

【００４０】
実施例８
２台の押出機が設けられた多層パリソン製造装置を用い、第１の押出機からポリエチレンテレフタレート（以下、ＰＥＴと略する）を、第２の押出機から実施例４で得たペレット４（バリア層）をそれぞれ射出し、ＰＥＴ層／バリア層／ＰＥＴ層の２種３層構成を有する多層パリソンを成形した。なお、多層パリソン中のバリア層の含有率は５ｗｔ％であった。
次いで、ブロー成形機を用いて上記多層パリソンを二軸延伸ブローして、寸法が全長２２３ｍｍ×外形６５ｍｍφ、表面積が０．０４ｍ^２、内容積が５００ｍｌ、底部形状がペタロイドタイプのボトル状容器を得た。このボトルの外観は無色透明であり、紫色を呈している部分は見られなかった。
【００４１】
比較例４
ペレット４の代わりにペレット８を使用したこと以外は実施例８と同様にして、ボトル状容器を得た。このボトルの外観は透明であるが、口部及び底部の部分が紫色を呈していた。
【００４２】
上記実施例から明らかなように、本発明の方法にて樹脂（Ａ）と酢酸コバルト・４水和物からなるペレットを製造し、これからシート状の成形品を得た実施例１乃至７では、酢酸コバルト・４水和物を添加していない比較例３と比較して、外観上差はなく、食品用包装容器向け包装材料として問題ないものであった。一方、常圧下で溶融混練したペレットを原料としてシートを製造した比較例１では、得られた製品の外観は紫色を呈しており、さらに酢酸臭がするものであったため、食品用包装材料として利用するには問題のあるものであった。また、ペレット製造時の減圧度が小さい比較例２では、酢酸臭は無かったものの、シートは紫色を呈しており、比較例１と同様に食品用包装材料として利用するには問題のあるものであった。
【００４３】
また実施例８に示したように、成形体形状がボトルであっても、本発明の製造方法により得られた成形体は食品用包装容器向け包装材料として問題ないものであった。一方、比較例４に示したように、常圧下で溶融混練したペレットを原料として製造したボトルは紫色を呈しており、食品用包装材料として利用するには問題のあるものであった。
【００４４】
【発明の効果】
本発明のポリアミド樹脂組成物の製造方法は、コバルト化合物由来の青色乃至紫色の着色が無い外観特性に優れた樹脂組成物および成形体を提供するものであり、工業的に優れたものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polyamide resin composition having an oxygen absorption function, and a molded article obtained therefrom. Specifically, the polyamide has excellent appearance characteristics as well as having an excellent oxygen absorption function, and has no coloration derived from a blue to purple cobalt compound, which has been a problem in a conventional polyamide resin composition having an oxygen absorption function. The present invention relates to a method for producing a resin composition and a molded body obtained from the resin composition.
[0002]
[Prior art]
Metal cans and glass bottles that were previously used as packaging containers that block the entry of oxygen from the outside and have excellent contents preservability are made of plastic that uses an oxygen-barrier thermoplastic resin in terms of processability and cost. An alternative to packaging containers is recommended. As the oxygen barrier thermoplastic resin, it has low permeability to gaseous substances such as oxygen and carbon dioxide gas, is easy to process, and is transparent and has sufficient mechanical strength. Polyamide (hereinafter abbreviated as nylon MXD6) obtained from polycondensation reaction of ethylene-vinyl alcohol copolymer or diamine component mainly composed of metaxylylenediamine and dicarboxylic acid component mainly composed of adipic acid is widely used. Has been. However, the packaging container made of metal or glass has substantially zero gas permeation from the outside of the container to the inside of the container. Gas permeation from the outside of the container to the inside of the container occurs at a level that cannot be ignored, and the gas permeation amount tends to increase depending on the environment in which the packaging container is stored. There was a problem with long-term storage.
[0003]
In recent years, a small amount of transition metal compound is added to nylon MXD6 and mixed to give nylon MXD6 an oxygen absorption function, and this is used as an oxygen barrier material constituting containers and packaging materials. Nylon MXD6 absorbs oxygen coming from the container and nylon MXD6 also absorbs oxygen remaining inside the container, so that a method to improve the storage stability of the contents over containers using conventional oxygen-barrier thermoplastic resin is put into practical use. It is being done.
[0004]
The manufacturing method of nylon MXD6 having an oxygen absorbing function is the master pellet by adhering the transition metal compound to the nylon MXD6 pellet by mixing the thermoplastic resin pellet containing nylon MXD6 and the solution containing the transition metal compound and then evaporating the solvent. (Refer to Patent Document 1) or a method of obtaining a master pellet by mixing a thermoplastic resin pellet containing nylon MXD6 and a transition metal compound, and then extruding a strand by melting and kneading using an extruder or the like to form a pellet. (See Patent Document 2). Nylon MXD6 having an oxygen absorbing function is mainly mixed with a cobalt compound containing cobalt metal, and these master pellets and molded articles obtained using the same are derived from the cobalt compound. Blue to purple coloring is observed. Although this coloration is relatively inconspicuous in a thin product such as a film, the above coloration can be seen when the film is wound into a roll, or polyethylene terephthalate and nylon MXD6 having an oxygen absorption function In a bottle having a multilayer structure in which each layer is laminated alternately, the thickness of the layer made of nylon MXD6 is thin on the bottle side wall, so the coloring is not conspicuous, but the thickness of the bottle bottom wall is relatively thick. Tend to stand out. The above-mentioned various packaging materials are assumed to be used for storage of beverages and foods, but blue and purple are generally unfavorable in appearance as food packaging materials and have excellent functions. However, it is assumed that it cannot be used as a food packaging container due to an appearance problem.
[0005]
[Patent Document 1]
Japanese National Patent Publication No. 2-500846
[Patent Document 2]
Japanese National Patent Publication No. 11-514385
[0006]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems, and to produce a polyamide resin composition having an oxygen absorption function excellent in appearance characteristics free from blue or purple coloring derived from a cobalt compound when processed into a molded body, and An object of the present invention is to provide a molded article using the resin composition.
[0007]
[Means for Solving the Problems]
As a result of intensive studies on the solution of the above problems, the present inventors have used cobalt acetate tetrahydrate as a cobalt compound, and this is a molten mixture of polyamide having a property of expressing an oxygen absorbing function such as nylon MXD6. Is produced using a specific production method, and various molded products are produced by using this, and a polyamide resin having an oxygen absorption function excellent in appearance characteristics in which blue to purple coloring, which has been a problem in the past, is not seen It has been found that a composition can be produced, and the present invention has been completed.
[0008]
That is, the present invention relates to a resin (A) mainly comprising a polyamide obtained by polycondensation with a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 50 mol% or more of adipic acid, and acetic acid. A method for producing a polyamide resin composition comprising cobalt tetrahydrate, comprising: mixing a resin (A) with cobalt acetate tetrahydrate After melt mixing or melt kneading, a temperature higher than 120 ° C. and (melting point of resin (A) −10 ° C.) or less, Under a pressure of 160 Torr or less Dry or solid state polymerization It is related with the manufacturing method of the polyamide resin composition characterized by performing.
[0009]
Moreover, this invention relates to the molded object formed using said polyamide resin composition.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. The polyamide resin composition of the present invention comprises a resin (A) mainly composed of polyamide obtained by polycondensation with a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 50 mol% or more of adipic acid. It is a polyamide resin composition comprising cobalt acetate tetrahydrate.
[0011]
Resin (A) is mainly composed of nylon MXD6 obtained by polycondensation with a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 50 mol% or more of adipic acid, and a cobalt compound When oxygen is added, it exhibits excellent oxygen absorption ability. Nylon MXD6 is obtained by polycondensation of a diamine component mainly composed of metaxylylenediamine and a dicarboxylic acid component mainly composed of adipic acid. Other components include paraxylylenediamine, 1 , 3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, tetramethylenediamine, hexamethylenediamine, nonamethylenediamine, 2-methyl-1,5-pentanediamine, suberic acid, azelaic acid, Sebacic acid, 1,10-decanedicarboxylic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid or the like may be copolymerized, or a carbon-carbon double bond partially introduced may be used. . Here, the diamine component preferably contains 70% by mole or more of metaxylylenediamine, and the dicarboxylic acid component preferably contains 50% by mole or more of adipic acid. When the metaxylylenediamine in the diamine component is 70 mol% or more, the polyamide resin obtained therefrom can exhibit excellent gas barrier properties. Further, when the adipic acid in the dicarboxylic acid component is 50 mol% or more, a decrease in gas barrier properties and the like can be avoided.
[0012]
The relative viscosity of nylon MXD6 (96 g sulfuric acid solution of 1 g / dl, 25 ° C.) is preferably 1.5 to 4.2, more preferably 1.8 to 4.0, and 2.0 to 3.7. Is more preferable. If the relative viscosity of the nylon MXD6 is within the above range, there is an advantage that various processes can be easily performed. Relative viscosity (1 g / dl 96% sulfuric acid solution, 25 ° C.) is the drop time at 25 ° C. measured with a Canon Fenceke viscometer after dissolving 1 g of resin in 100 cc (1 dl) of 96% sulfuric acid. It is the ratio of the drop time (t0) in 96% sulfuric acid measured in the same manner as (t), and is represented by the following equation.
Relative viscosity = (t) / (t0)
[0013]
As long as the resin (A) is mainly composed of a nylon MXD6 structural unit, a carbon-carbon double bond may be introduced into the molecular chain, and other thermoplastic resins are blended. It may be what was done. Examples of the thermoplastic resin that can be blended include polyamides other than nylon MXD6 such as nylon 6, nylon 66, nylon 666, nylon 610, nylon 6T, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyethylene and polypropylene, etc. Examples thereof include polymers such as polyolefin, polycarbonate, polystyrene, and thermoplastic elastomer.
[0014]
Furthermore, in the present invention, a phosphorus compound is added to the resin (A) in order not to impair the effects of the present invention, in order to increase the processing stability during melt molding or to prevent the resin (A) from being colored. You may do it. As the phosphorus compound, known substances capable of exhibiting the above-mentioned functions can be used without limitation, but phosphorus compounds containing alkali metals or alkaline earth metals are preferably used. For example, phosphoric acid such as sodium, magnesium, calcium, etc. Examples include salts, hypophosphites, and phosphites. In the present invention, the one using an alkali metal or alkaline earth metal hypophosphite as the phosphorus compound is preferably used because of its particularly excellent anti-coloring effect. The phosphorus atom concentration is preferably 400 ppm or less, and more preferably 200 ppm or less. When the phosphorus atom concentration exceeds 400 ppm, it may take time until the oxygen absorption function of the polyamide resin composition of the present invention is exhibited.
[0015]
Furthermore, the resin (A) includes pigments, dyes, lubricants, matting agents, heat stabilizers, weather stabilizers, ultraviolet absorbers, nucleating agents, plasticizers, flame retardants, antistatic agents, anti-coloring agents, alkaline compounds, etc. It is possible to add additives such as anti-gelling agents exemplified in the above, and fillers such as clay, mica, glass fiber, zeolite, layered silicate, etc., but the resin ( A) can be a mixture of various materials.
[0016]
In the present invention, cobalt acetate tetrahydrate is used as the catalyst for promoting the oxidation reaction of the resin (A). The reason for using cobalt acetate tetrahydrate in the present invention is that when this compound is added to the resin (A) and a molded product is produced in a specific production process described later, the blue or purple color characteristic of the cobalt compound is obtained. It can be mentioned that there is no difference in appearance from the molded body to which no cobalt compound is added. The reason why the coloration peculiar to cobalt compounds disappears is not clear, but cobalt acetate tetrahydrate decomposes into cobalt ions and acetic acid during melt processing, but acetic acid can be exposed by exposure to specific temperatures and pressures as in the present invention. Is removed from the system, so that the decomposition of cobalt acetate tetrahydrate is promoted, and it is presumed that the cobalt ions change to a state in which the above color is not developed. Cobalt contained in the compound accelerates the oxidation reaction of the polyamide and develops the oxygen absorbing function of the polyamide. The oxidation of polyamide caused by cobalt is caused by the generation of radicals due to the extraction of hydrogen atoms from the methylene chain adjacent to the allylene group of the polyamide by cobalt, the generation of peroxy radicals by the addition of oxygen molecules to the radicals, the peroxy radicals It is thought that this is caused by the extraction of the hydrogen atom by, and the above reactions. Further, since the compound is an alkaline compound containing acetic acid, the reaction rate of the three-dimensional reaction that tends to occur during the melt processing of the resin (A) containing nylon MXD6 as a main component is reduced. It is possible to obtain a molded article having a good appearance characteristic with few gel-like materials such as eyes.
In addition, as a cobalt compound which does not exhibit purple and blue coloring, cobalt oxide is mentioned, for example, However, Cobalt oxide is inferior in the catalyst function compared with another cobalt compound, Furthermore, resin (it has nylon MXD6 as a main component ( Since there is no function to prevent gelation of A), its usefulness is low as compared with the cobalt acetate tetrahydrate used in the present invention.
[0017]
In the present invention, the amount of cobalt acetate tetrahydrate mixed with the resin (A) is preferably in the range of 10 to 5000 ppm as the cobalt atom concentration relative to the resin (A). When the metal atom is less than 10 ppm, the resulting polyamide resin composition does not sufficiently exhibit the oxygen absorption function. Moreover, when it is more than 5000 ppm, oxidation deterioration of the resin (A) may occur in the production process of the polyamide resin composition, and a purple color derived from cobalt acetate tetrahydrate may remain in the molded body. Absent.
[0018]
Next, the manufacturing method of the polyamide resin composition of this invention is demonstrated. In the present invention, the molten mixture of the resin (A) constituting the polyamide resin composition and cobalt acetate tetrahydrate is subjected to at least one heat treatment selected from melt kneading, drying and solid phase polymerization under a pressure of 160 Torr or less. Is obtained. The said molten mixture refers to the thing in a molten state or the solid state melt-mixed.
[0019]
As the melt-kneading method, a resin (A) and cobalt acetate tetrahydrate previously melt-mixed, or a resin (A) and cobalt acetate tetrahydrate each or dry-mixed are used as an extruder. A method of supplying and melt-kneading under a pressure of 160 Torr or less. As the extruder, various extruders such as a single-screw extruder and a twin-screw extruder can be used, and among these, an extruder equipped with a vacuum pump is preferable, and a twin-screw extrusion having a particularly high surface renewal capability. A machine is preferably used. By using the above extruder, acetic acid generated by decomposition of cobalt acetate tetrahydrate is easily removed from the system. The resin temperature during melt kneading is preferably higher than the melting point of the resin (A) and lower than (the melting point + 60 ° C.). By performing melt-kneading so that the resin temperature is within the above range, cobalt acetate tetrahydrate can be uniformly mixed in the resin (A), and a product with less gelled product can be obtained.
[0020]
As a drying method, a resin (A) and a cobalt acetate tetrahydrate previously melt-mixed at a pressure of 160 Torr or lower and higher than 120 ° C. (resin (A) melting point−10 ° C.) or lower are used. The method of drying at temperature is mentioned. Usable devices include heatable dryers equipped with vacuum devices such as vacuum pumps and aspirators, rotary drum type devices called tumble dryers, conical dryers, rotary dryers, etc., and Nauter mixers. Examples thereof include a conical one provided with a rotating blade inside, but are not limited thereto, and any one that can be heated under the above pressure can be used. As for the temperature at the time of heating, the effect of the present invention can be obtained in a shorter time as the temperature is higher. However, when heated at a temperature higher than 10 ° C. lower than the melting point of the resin (A), the resin is fused and the product May not be able to get. On the other hand, when the temperature is lower than 120 ° C., the acetic acid generated by the decomposition of cobalt acetate tetrahydrate becomes difficult to be removed from the system, and a purple color may be seen in a molded product obtained by using this. is there. This method often takes a relatively long time because the molten mixture is in a solid state. Therefore, when performing this method, it is preferable that the inside of the system is replaced with an inert gas such as nitrogen and then dried under reduced pressure because the coloring of the polyamide resin composition can be prevented. Moreover, the composition obtained by the above-mentioned melt-kneading method can be further dried by this method.
[0021]
The polyamide resin composition of the present invention can be subjected to solid phase polymerization after melt mixing or melt kneading to increase the molecular weight. In solid phase polymerization, the decompression conditions, the solid phase polymerization time, the solid phase polymerization temperature, etc. can be arbitrarily set depending on the molecular weight of the target polyamide, but when melt kneading is performed at a pressure higher than 160 Torr, it is 160 Torr or less. It is preferable to carry out solid phase polymerization at a temperature higher than 120 ° C. and lower than (melting point of resin (A) −10 ° C.) under the pressure of Solid phase polymerization can be performed by a known method. For example, a method in which a polyamide resin composition is charged into a tumbler (rotary vacuum tank) or a nauta mixer (conical heating device having a rotating blade inside) and the like, and is performed by a batch operation, a polyamide resin composition and heated nitrogen Examples thereof include, but are not limited to, a tower-type continuous solid phase polymerization method in which a gas is continuously contacted.
[0022]
By adopting a production method including such a heat treatment, it becomes possible to obtain a molded body with less blue or purple coloring.
[0023]
In each of the above-described methods for producing a polyamide resin composition, the internal pressure at the time of performing at least one heat treatment selected from melt kneading, drying and solid phase polymerization is preferably 160 Torr or less, more preferably 110 Torr or less, and further Preferably it is 60 Torr or less. A system pressure higher than 160 Torr is not preferable because blue or purple coloring may remain in the molded body or an acetic acid odor may be generated from the molded body. When performing a plurality of the above heat treatments, the heat treatment may be performed at a pressure of 160 Torr or less during at least one heat treatment.
[0024]
The polyamide resin composition produced by the method of the present invention can be used after being processed into molded articles such as various packaging materials and packaging containers. The packaging material can be processed into a film-like or sheet-like molded body, and the packaging container constitutes at least a part of bottles, trays, cups, tubes, various pouches such as flat bags and standing pouches, etc. Can be used as a material. Further, the packaging material or the packaging container may have a single layer made of the polyamide resin composition obtained in the present invention or a multilayer structure combined with other thermoplastic resins. In order to improve the properties, polyamide resin compositions include polyamides represented by nylon 6 and nylon 66, polyesters represented by polyethylene terephthalate and polybutylene terephthalate, polyolefins represented by polyethylene and polypropylene, and polystyrene. Further, various thermoplastic resins such as polycarbonate and ethylene vinyl alcohol copolymer can be mixed and used. These mixtures can also be used for packaging materials and packaging containers. In the packaging material or packaging container using the polyamide resin composition of the present invention, the thickness of the layer using the polyamide is not particularly limited, but the layer is formed to have a thickness of 1 μm or more. It is preferable to do.
[0025]
A well-known method can be utilized about the manufacturing method of the packaging material and packaging container which utilize the polyamide resin composition of this invention. For example, the film, sheet, or tube-shaped packaging material can be molded by extruding the polyamide melted through a T die, a circular die or the like from an attached extruder. In addition, the film-form molded object obtained by the above-mentioned method can also be processed into a stretched film by extending | stretching this. A bottle-shaped packaging container can be obtained by injecting molten polyamide resin into a mold from an injection molding machine to manufacture a preform, and then heating to a stretching temperature and blow-stretching. Containers such as trays and cups are obtained by injecting the polyamide melted into the mold from an injection molding machine, or by forming a sheet-like packaging material by a molding method such as vacuum molding or pressure molding. be able to. The packaging material and the packaging container using the polyamide resin composition of the present invention can be manufactured through various methods without depending on the above-described manufacturing method.
[0026]
Various articles can be stored and stored in the packaging container using the polyamide resin composition of the present invention. For example, carbonated drinks, juice, water, milk, sake, whiskey, shochu, coffee, tea, jelly drinks, health drinks, etc. Seasonings such as jams, creams, chocolate pastes and other paste-like foods, liquid soups, boiled foods, pickles, stewed and other liquid processed foods such as buckwheat noodles, noodles, ramen and other raw noodles and boiled noodles , Representatives of pre-cooked rice such as polished rice, moistened rice, and non-washed rice, cooked cooked rice, processed rice products such as gomoku rice, red rice, rice bran, powdered soup, and powdered seasonings such as dashi stock High-moisture foods, dried vegetables, coffee beans, coffee powder, tea, low-moisture foods such as confectionery made from grains, and other solid and solution chemicals and liquids such as agricultural chemicals and insecticides And pasty medicines, lotions, makeup creams, cosmetic milky lotion, hair dressing, it is possible to house a hair dye, shampoo, soap, detergent or the like, various articles.
[0027]
【Example】
The present invention will be described more specifically below. However, the present invention is not limited to the following examples.
[0028]
Example 1
Polyamide 1 (relative viscosity; 2.6) obtained by melt polycondensation of adipic acid and metaxylylenediamine and cobalt acetate tetrahydrate weighed so that the cobalt metal concentration is 350 ppm were mixed with a tumbler. Then, this mixture was melt-kneaded at a resin temperature of 270 ° C. while maintaining the pressure in the cylinder at 110 Torr with a twin-screw extruder with a vacuum vent of 35 mmφ in the cylinder diameter, the strand was extruded from the strand die, and transferred to the net belt while cooling with air. And pelletized with a pelletizer to produce pellets 1 of 2.5 mmL × 2.5 mmφ.
Next, using a multilayer sheet manufacturing apparatus equipped with three extruders, a feed block, a T die, a take-up device, etc., polypropylene (hereinafter abbreviated as PP) is transferred from the first extruder to the second extruder. The maleic anhydride-modified polypropylene (hereinafter abbreviated as AD) is extruded from the third extruder, and the pellet 1 (barrier layer) is extruded from the third extruder, and PP (350 μm) / AD (20 μm) / barrier layer (40 μm) / AD. A multilayer sheet having a layer configuration of (20 μm) / PP (350 μm) was produced, and was wound up by about 50 m with a winder. The appearance of the sheet roll was colorless and transparent, and no blue or purple portion was observed.
[0029]
Example 2
After mixing polyamide 1 and cobalt acetate tetrahydrate with a tumbler in the same manner as in Example 1, this mixture was melted at a resin temperature of 268 ° C. in a single-screw extruder with a cylinder diameter of 30 mmφ under normal pressure. After kneading, the strand was extruded from a strand die, cooled with water, and then pelletized with a pelletizer to produce a 2.5 mmL × 2.5 mmφ pellet. Next, this pellet was vacuum-dried at 150 ° C. for 6 hours under a pressure of 1 Torr or less using a vacuum dryer attached with a vacuum pump to obtain pellet 2.
Next, PP (350 μm) / AD (20 μm) / barrier layer (40 μm) / AD (20 μm) / PP (350 μm) was obtained in the same manner as in Example 1 except that pellet 2 was used instead of pellet 1. A multilayer sheet having a layer structure was produced and wound up by about 50 m with a winder. The appearance of the sheet roll was colorless and transparent, and no blue or purple portion was observed.
[0030]
Example 3
Pellets 3 were produced in the same manner as in Example 1 except that the pressure in the cylinder at the time of extrusion was 60 Torr.
Next, PP (350 μm) / AD (20 μm) / barrier layer (40 μm) / AD (20 μm) / PP (350 μm) was obtained in the same manner as in Example 1 except that pellet 3 was used instead of pellet 1. A multilayer sheet having a layer structure was produced and wound up by about 50 m with a winder. The appearance of the sheet roll was colorless and transparent, and no blue or purple portion was observed.
[0031]
Example 4
Pellets were produced in the same manner as in Example 1 except that the pressure in the cylinder at the time of extrusion was 360 Torr. This pellet was vacuum-dried at 150 ° C. for 6 hours under a pressure of 1 Torr or less using a vacuum dryer attached with a vacuum pump to obtain pellet 4.
Next, PP (350 μm) / AD (20 μm) / barrier layer (40 μm) / AD (20 μm) / PP (350 μm) was obtained in the same manner as in Example 1 except that pellet 4 was used instead of pellet 1. A multilayer sheet having a layer structure was produced and wound up by about 50 m with a winder. The appearance of the sheet roll was colorless and transparent, and no blue or purple portion was observed.
[0032]
Example 5
After mixing polyamide 2 (relative viscosity; 2.1) obtained by polycondensation of adipic acid and metaxylylenediamine with cobalt acetate tetrahydrate weighed to a cobalt metal concentration of 350 ppm with a tumbler The mixture is melt-kneaded at a resin temperature of 270 ° C. under normal pressure in a single-screw extruder with a cylinder diameter of 30 mmφ, the strand is extruded from a strand die, cooled with water, pelletized with a pelletizer, and 2.5 mm L A pellet of × 2.5 mmφ was produced. Next, the pellet is placed in a 3 L glass eggplant flask and connected to an evaporator equipped with a vacuum pump, thermocouple, and nitrogen inlet tube, and the inside of the eggplant flask is sufficiently purged with nitrogen. It was attached to the bath and the internal temperature was raised to 150 ° C. over 60 minutes. Next, the pressure in the eggplant flask was reduced to 1 Torr or less, and the internal temperature was further increased to 190 ° C. over 60 minutes, and then the internal temperature was maintained at 190 ° C. for 30 minutes to perform solid phase polymerization. Then, the eggplant flask was taken out from the oil bath, and after introducing nitrogen, the pellet was cooled to room temperature under a small amount of nitrogen stream to obtain pellet 5. The relative viscosity of the polyamide after solid phase polymerization was 2.6.
Next, PP (350 μm) / AD (20 μm) / barrier layer (40 μm) / AD (20 μm) / PP (350 μm) was obtained in the same manner as in Example 1 except that pellet 5 was used instead of pellet 1. A multilayer sheet having a layer structure was produced and wound up by about 50 m with a winder. The appearance of the sheet roll was colorless and transparent, and no blue or purple portion was observed.
[0033]
Example 6
Pellets 6 were produced in the same manner as in Example 1 except that the amount of cobalt acetate tetrahydrate added was such that the cobalt concentration was 1000 ppm.
Next, using a multilayer sheet manufacturing apparatus equipped with three extruders, a feed block, a T die, a take-up device, etc., polypropylene (hereinafter abbreviated as PP) is transferred from the first extruder to the second extruder. Then, maleic anhydride-modified polypropylene (hereinafter abbreviated as AD) was extruded from the third extruder, and 40 parts by weight of the pellet 6 and 60 parts by weight of the polyamide 1 mixture (barrier layer) were each extruded into PP (350 μm). A multilayer sheet having a layer structure of / AD (20 μm) / barrier layer (40 μm) / AD (20 μm) / PP (350 μm) was produced, and wound by about 50 m with a winder. The appearance of the sheet roll was colorless and transparent, and no blue or purple portion was observed.
[0034]
Example 7
Pellets 7 were produced in the same manner as in Example 1 except that the amount of cobalt acetate tetrahydrate added was such that the cobalt concentration was 2000 ppm.
Next, using a multilayer sheet manufacturing apparatus equipped with three extruders, a feed block, a T die, a take-up device, etc., polypropylene (hereinafter abbreviated as PP) is transferred from the first extruder to the second extruder. Then, maleic anhydride-modified polypropylene (hereinafter abbreviated as AD) is extruded from the third extruder, and 20 parts by weight of the pellet 7 and 80 parts by weight of the polyamide 1 mixture (barrier layer) are extruded into PP (350 μm). A multilayer sheet having a layer structure of / AD (20 μm) / barrier layer (40 μm) / AD (20 μm) / PP (350 μm) was produced, and wound by about 50 m with a winder. The appearance of the sheet roll was colorless and transparent, and no blue or purple portion was observed.
[0035]
Comparative Example 1
A pellet 8 was prepared in the same manner as in Example 1 except that the pressure in the cylinder at the time of extrusion was normal pressure (760 Torr), and PP (350 μm) / AD (20 μm) / barrier layer (40 μm) / AD (20 μm). ) / PP (350 μm) layered sheet was produced and wound up by about 50 m with a winder. The appearance of the sheet roll was transparent but exhibited a purple color. In addition, there was a slight acetic acid odor during the manufacture of the sheet roll and in the product obtained.
[0036]
Comparative Example 2
Pellets 9 were prepared in the same manner as in Example 1 except that the pressure in the cylinder during extrusion was 360 Torr, and PP (350 μm) / AD (20 μm) / barrier layer (40 μm) / AD (20 μm) / PP ( A multilayer sheet having a layer configuration of 350 μm was manufactured and wound up by about 50 m with a winder. The appearance of the sheet roll was transparent, but had a light purple color.
[0037]
Comparative Example 3
Using the polyamide 1 obtained in Example 1, a multilayer sheet having a layer structure of PP (350 μm) / AD (20 μm) / barrier layer (40 μm) / AD (20 μm) / PP (350 μm) is produced and wound. About 50 m was taken up with a take-off machine. The appearance of the sheet roll was colorless and transparent.
[0038]
[Table 1]

[0039]
[Table 2]

[0040]
Example 8
Using a multi-layer parison manufacturing apparatus provided with two extruders, polyethylene terephthalate (hereinafter abbreviated as PET) from the first extruder, and pellets 4 (barrier) obtained in Example 4 from the second extruder Each layer) was injected to form a multilayer parison having a PET layer / barrier layer / PET layer type 2 layer 3 layer configuration. In addition, the content rate of the barrier layer in a multilayer parison was 5 wt%.
Next, the multilayer parison is biaxially stretched and blown using a blow molding machine, and the dimensions are 223 mm in total length × 65 mm in outer diameter, and the surface area is 0.04 m. ² A bottle-shaped container having an internal volume of 500 ml and a petaloid type bottom was obtained. The appearance of this bottle was colorless and transparent, and no purple portion was seen.
[0041]
Comparative Example 4
A bottle-shaped container was obtained in the same manner as in Example 8, except that pellet 8 was used instead of pellet 4. The appearance of this bottle was transparent, but the mouth and bottom were purple.
[0042]
As is clear from the above examples, pellets made of resin (A) and cobalt acetate tetrahydrate were produced by the method of the present invention, and in Examples 1 to 7 in which sheet-like molded products were obtained, Compared with Comparative Example 3 in which cobalt acetate tetrahydrate was not added, there was no difference in appearance, and there was no problem as a packaging material for food packaging containers. On the other hand, in Comparative Example 1 in which a sheet was manufactured using pellets melt-kneaded under normal pressure as raw materials, the obtained product had a purple appearance and further had an acetic acid odor, and thus was used as a packaging material for food. There was a problem to do. Further, in Comparative Example 2 where the degree of decompression at the time of pellet production was small, although there was no acetic acid odor, the sheet had a purple color, which was problematic for use as a food packaging material as in Comparative Example 1. there were.
[0043]
Further, as shown in Example 8, even if the shape of the molded body was a bottle, the molded body obtained by the production method of the present invention had no problem as a packaging material for food packaging containers. On the other hand, as shown in Comparative Example 4, a bottle produced using pellets melted and kneaded under normal pressure as a raw material had a purple color and had a problem in use as a food packaging material.
[0044]
【The invention's effect】
The method for producing a polyamide resin composition of the present invention provides a resin composition and a molded article excellent in appearance characteristics free from a blue to purple coloration derived from a cobalt compound, and is industrially excellent.

Claims (3)

Resin (A) based on polyamide obtained by polycondensation with a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 50 mol% or more of adipic acid, and cobalt acetate tetrahydrate And a mixture of the resin (A) and cobalt acetate tetrahydrate is melt-mixed or melt-kneaded at a temperature higher than 120 ° C. (the melting point of the resin (A) −10). C.) a method for producing a polyamide resin composition, wherein drying or solid phase polymerization is carried out at a temperature of not more than 160 ° C. and a pressure of not more than 160 Torr. 2. The method for producing a polyamide resin composition according to claim 1, wherein the resin temperature during melt kneading is not less than the melting point of the resin (A) and not more than (the melting point + 60 ° C.). The method for producing a polyamide resin composition according to claim 1, wherein the addition amount of cobalt acetate tetrahydrate is 10 to 5000 ppm as a cobalt atom concentration relative to the resin (A).