JPS6255498B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polyester hollow container that has a pearl-like surface gloss and is excellent in mold reproducibility and drop strength during blow molding. Polyethylene terephthalate has excellent mechanical properties and chemical resistance, and has a relatively low permeability to gases such as oxygen and carbon dioxide, and has excellent transparency, so it is used in containers for foods, beverages, cosmetics, etc., and molded products. An attempt is being made to do so. In particular, it is attracting attention for its use in cosmetic containers, caps, compacts, etc. because it has excellent fragrance retention and chemical resistance, and does not alter the quality of the contents. For such uses, not only molded products with excellent transparency but also molded products with excellent decorative properties, such as those with pearl-like surface gloss and excellent appearance, are increasingly required. Conventionally, a method of adding pearl pigments to thermoplastic resin is known as a method of imparting pearl-like surface gloss to plastic molded products, but there are problems with the toxicity of pearl pigments, insufficient pearl appearance, and resistance at low temperatures. It has the disadvantage that it has a problem with impact resistance and is difficult to put into practical use. Furthermore, methods are known for molding specific thermoplastic resin mixtures, such as mixtures of polycarbonate and polymethyl methacrylate, or mixtures of styrene resin and methacrylate resin, but molding by such methods has poor chemical resistance. Its uses are limited due to its low strength and low mechanical strength. On the other hand, injection molded products obtained using a mixture of polyester resin and other polymers such as polystyrene, polyethylene, polycarbonate, polyamide, etc. exhibit almost no pearl-like surface gloss and have no external appearance from a decorative standpoint. There is no such thing. Under these circumstances, the present inventors used a resin composition consisting of a polyester resin and a methacrylic resin having an intrinsic viscosity within a specific range, and carried out injection molding under specific injection molding conditions to achieve consistently excellent appearance. We discovered that injection molded products with a pearl-like surface gloss can be obtained, and filed a patent application. However, although injection molded products obtained using such resin compositions have excellent pearl-like surface gloss, hollow containers obtained by blow molding a bottomed preform, which is one form of injection molded products, have excellent pearl-like surface gloss. Although it had a pearl-like surface gloss, it was found that the reproducibility of the mold during blow molding was poor, and furthermore, the drop strength was poor. In view of the current situation, the present inventors conducted intensive studies to obtain a hollow container with excellent mechanical strength and reproducibility according to the mold during blow molding, and a pearl-like surface gloss with excellent decorative properties. A resin composition consisting of a thermoplastic polyester resin having an inherent viscosity and a methacrylic resin copolymerized with a specific amount of a specific acrylic acid ester is injection molded under specific conditions to obtain a bottomed prebody, which is then blow molded. The present inventors have discovered that a hollow container that satisfies the above objectives can be obtained by doing so, and have arrived at the present invention. That is, the gist of the present invention is that the main repeating unit is ethylene terephthalate, and the intrinsic viscosity is
At least one kind of acrylic ester represented by the following formula CH ₂ =CHCOOR (in the formula, R is an alkyl group having 1 to 8 carbon atoms) to 5 to 40 thermoplastic polyester resins having a molecular weight of 0.75 to 1.40 and methyl methacrylate. Injection molding of a resin composition consisting of a methacrylic resin copolymerized by weight% under the conditions that the linear velocity of the resin composition moving in the mold during injection molding is 10 mm/sec or more and the mold temperature is 55°C or less. and the thickness is 0.5
A method for manufacturing a polyester hollow container, which comprises forming a preformed body with a bottom of ~10 mm and then blow molding it. The thermoplastic polyester resin used in the present invention is one in which 75 mol% or more of the repeating units that constitute it consist of ethylene terephthalate, and the copolymerized components include isophthalic acid, adipic acid, sebacic acid, and P-β-oxyethoxybenzoic acid. acid, dicarboxylic acid components such as diphenyl ether-4,4'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, etc. or their alkyl ester derivatives, propylene glycol, butanediol, hexamethylene glycol, neo Glycols such as pentyl glycol and cyclohexanedimethanol are used. As the thermoplastic polyester resin, a polymer obtained by either a method of performing polycondensation through transesterification or a method of directly performing polycondensation through esterification can be used, but its intrinsic viscosity [η] teeth
It needs to be in the range of 0.75 to 1.40. A polymer having a high intrinsic viscosity can be obtained by a known solid phase polymerization method using a polymer obtained by the above-mentioned conventional polymerization method. If the intrinsic viscosity is less than 0.75, the mechanical strength of the hollow container will be low, and at the same time pearl-like surface gloss will develop slightly or hardly at all, which is not preferable. Further, when the intrinsic viscosity exceeds 1.40, a strong pearl-like surface luster is developed, but moldability becomes extremely difficult and the desired hollow container cannot be formed, which is not preferable. Note that the intrinsic viscosity [η] is a value determined from the solution viscosity measured at 25° C. in a phenol/tetrachloroethane=50/50 (weight ratio) solution. The methacrylic resin in the present invention is an acrylic ester of methyl methacrylate represented by CH ₂ =CHCOOR (in the formula, R is an alkyl group having 1 to 8 carbon atoms), that is, methyl acrylate, ethyl acrylate, (iso)propyl acrylate,
(iso)butyl acrylate, acrylic acid (iso)
It is a copolymer of at least one of pentyl, (iso)hexyl acrylate, (iso)heptyl acrylate, (iso)octyl acrylate, etc. within a range of 5 to 40% by weight. In the present invention, it is not preferable that the alkyl group in the acrylic ester represented by the above formula exceeds 8 carbon atoms because the properties as a methacrylic resin deteriorate and it is impossible to form the intended hollow container. In addition, the amount of acrylic ester copolymerized with methyl methacrylate must be within the range of 5 to 40% by weight, and the amount of copolymerized acrylic ester must be 5 to 40% by weight.
If it is less than % by weight, there is no problem in terms of the development of pearly surface gloss, but it is not preferable because mold reproducibility during blow stretching is poor and only hollow containers with low drop strength can be obtained. On the other hand, if the amount of copolymerized acrylic ester exceeds 40% by weight, the fluidity of the methacrylic resin itself will be poor, and it will also be difficult to mix it with the thermoplastic polyester resin, resulting in the pearl-like shape that is the object of the present invention. This is not preferable since it is not possible to form a hollow container with surface gloss and excellent mold reproducibility and drop strength. When carrying out the present invention, the thermoplastic polyester resin and the methacrylic resin may be blended in any ratio, but the thermoplastic polyester resin is 51 to 99% by weight, and the methacrylic resin is 49 to 99% by weight.
When using a resin composition consisting of 1% by weight, the pearl-like surface gloss that characterizes the present invention is fully expressed, and it also has excellent chemical resistance and mechanical properties, especially impact resistance and drop strength, and is resistant to blow blows. This is particularly preferred since it allows a hollow container with extremely excellent mold reproducibility during stretching. In carrying out the present invention, additives such as dyes and pigments, ultraviolet absorbers, antistatic agents, nucleating agents, etc. may be added to the resin composition consisting of the thermoplastic polyester resin and methacrylic resin to the extent that they do not depart from the purpose of the present invention. It does not matter if it is blended. The above thermoplastic polyester resin and methacrylic resin can be blended by thoroughly mixing the respective resin powders and pellets in a mixer and then pelletizing them using an extruder, or by directly feeding these resin powders and pellets into an extruder and directly forming them into pellets. Any conventional method such as molding may be used. The present invention produces a bottomed preform that has a pearl-like surface gloss by injection molding the above-mentioned specific resin composition to form a bottomed preform and then blow-molding it. To achieve this, it is important to produce a bottomed preform under specific injection molding conditions. The injection molding conditions for creating the bottomed preform are described below in detail.
First, the most important factor is that the resin composition poured into the mold during injection molding is subjected to strong shear stress near the mold surface. Due to the strong shear stress during injection molding, the methacrylic resin particles in the resin composition are oriented in the flow direction of the resin, resulting in pearl-like surface gloss. In order for the methacrylic resin particles to be oriented in a specific direction by such shear stress, the linear velocity of the resin composition moving within the mold during injection molding should be 10 mm/sec or more, preferably 20 mm/sec or more. Needs to be injection molded. If the linear velocity of the resin composition in the mold is less than 10 mm/sec, pearl-like surface gloss will hardly appear, or even if it does, it will only appear around the gate of the molded product. Even if a preformed body with a bottom is blow-molded, it is not possible to obtain a hollow container having a profound feeling and a unique pearl-like surface luster, which is the object of the present invention. Here, the linear velocity is expressed as linear velocity = L/t (mm/sec), where L is the maximum flow length (mm) that the resin moves within the mold, and t is the injection time. is expressed as the time (seconds) it takes for the screw to travel 90% of the injection stroke. Furthermore, in the present invention, regulation of the mold temperature during injection molding is one of the important structural requirements to ultimately obtain a good hollow container. Polyester resins are usually molded at a mold temperature of 80°C or higher to promote crystallization, but in the present invention, on the contrary, the mold temperature is 55°C, which is the temperature indicated by the mold surface temperature immediately before molding. It is necessary that the bottomed preform be molded at a temperature below .degree. C., preferably below 40.degree. Mold temperature is 55
If the temperature exceeds °C, even if the linear velocity condition of the resin composition in the mold is satisfied, the pearl-like surface gloss of the bottomed preform will deteriorate, and as a result, the object of the present invention will be obstructed. It cannot be made into a hollow container. On the other hand, the thickness of the bottomed preform also affects the pearl appearance of the preform, which ultimately affects the pearl appearance of the final product, the hollow container. The bottomed preform must be injection molded to a thickness of 0.5 to 10 mm, preferably 1.5 to 6.0 mm. In this case, the bottomed preform has a heavy pearl-like surface gloss. exhibits. If the bottomed preform is injection molded to be thinner than 0.5 mm, the surface will have a pearl-like luster and a strong flowing pattern.
It may become mottled or become more transparent. Furthermore, if the bottomed preform is injection molded to a thickness of more than 10 mm, the pearl-like surface gloss will hardly appear and sink marks will occur easily. Even if such a bottomed preform is blow-molded, it cannot be made into a hollow container as the object of the present invention. As mentioned above, the linear velocity of the resin in the mold during injection molding, the mold temperature, and the wall thickness of the molded product are important factors for the development of the pearl-like surface gloss of the bottomed preform, but they are also important factors for the development of pearl-like surface gloss. Considering the relationship with the injection molding temperature, there is an optimum temperature range for developing pearlescent luster relative to the injection molding temperature. If the molding temperature is such that the resin temperature of the mixture is higher than 320°C, the development of pearlescent luster will be relatively low. When the polyester resin is a homopolymer, the molding temperature is preferably in the range of 270 to 300°C in terms of resin temperature. On the other hand, it is preferable that the residence time of the resin in the cylinder be as short as possible within a range that allows sufficient plasticization.
The influence of injection pressure on pearlescent luster development is small. The hollow container according to the present invention uses a methacrylic resin copolymerized with an acrylic acid ester as described above, and has three characteristics: the linear velocity of the resin in the mold during injection molding, the mold temperature, and the wall thickness of the bottomed preform. Blow molding is performed on a bottomed preform that has been injection molded under conditions that satisfy the conditions, and the blow molding method can be divided into the so-called in-jection blow method and the biaxial stretch blow method. Among these, the biaxial stretching blowing method may be a hot parison method or a cold parison method. The hollow container obtained by the method of the present invention has a more excellent pearl-like surface gloss when the bottomed preform injection molded under the above conditions is blow molded by a biaxial stretching blow method. has. That is, the bottomed preform has a stretching temperature of 80 to 160°C,
When biaxial stretch blow molding is carried out at a total stretching ratio of 1.3 to 20, the mechanical properties of the resulting hollow container are further improved, and a pearl-like surface gloss with a solid three-dimensional flow pattern is developed. It is particularly preferred for use in cosmetics. Hereinafter, a manufacturing method example of the present invention using the above-mentioned biaxial stretch blow molding method will be specifically explained. The stretching temperature is defined by the outer surface temperature of the bottomed preform immediately before biaxial stretch blow molding, and the inner surface temperature of the preform must also be within the above temperature range. . If blow molding is performed at a temperature below 80°C, stretching will occur partially, resulting in uneven wall thickness and a molded product with poor mold reproducibility. Further, blow molding at a temperature exceeding 160° C. is not preferred because it is difficult to achieve sufficient orientation and the molded product has extremely low mechanical strength such as drop strength. In order to maintain the bottomed preform within the above stretching temperature range, the bottomed preform obtained by injection molding may be left to cool, or the high temperature preform may be cooled to about room temperature. Any suitable method may be used, such as a method of uniformly heating the preform while rotating it with a far-infrared heater or the like after cooling. The above-mentioned total stretching ratio is defined as follows. That is, the ratio of the stretched and oriented vertical size of the biaxially stretch blow-molded hollow container to the substantially unoriented vertical size of the bottomed preform corresponding to this vertical direction is R ₁ , and The ratio between the stretch-oriented lateral size of a biaxially stretch-blow-molded hollow container and the substantially unoriented lateral size of the bottomed preform corresponding to this lateral direction.
Assuming R ₂ , the total stretching ratio is expressed as R ₁ ×R ₂ . In the present invention, the above-mentioned biaxial stretch blow molding method is particularly preferable because it can develop a unique three-dimensional flow pattern and a pearl-like surface gloss that is different from conventional methods and has excellent decorative properties. . In addition, the reproducibility of mold alignment during blow molding is excellent, and the hollow container has excellent drop strength. Examples of uses of the hollow container include cosmetic bottles for hair tonics, hair oils, cosmetic creams, lotions, cosmetic emulsions, perfumes, and even shampoos.
Suitable as a toiletry container for rinse, deodorizing liquid, etc. The present invention will be specifically explained below using Examples. The drop strength of the molded containers in Examples and Comparative Examples was tested using the following method. Drop test method (1) Aging at 40℃ for 1 month (2) Filling with commercially available hair tonic (3) Dropping method After aging, the hair tonic in the molded container was replaced with ice water at 0℃, and placed in ice water for 15 minutes. Soak. Thereafter, the molded container was dropped onto concrete from a height of 1 m alternately in the vertical and horizontal directions 10 times each. If the product does not break after falling from 1m, drop it from 2m in the same way. Repeat this operation for 3m, 4m, etc. The degree of damage caused by the height of the fall was defined as the fall strength. Examples 1 to 19, Comparative Examples 1 to 10 Methyl methacrylate (hereinafter abbreviated as MMA)
Table 1 shows methacrylic resins (hereinafter referred to as PMMA) having various copolymerization ratios of methyl acrylate (hereinafter referred to as MA) and polyethylene terephthalate having various intrinsic viscosities as shown in Table 1. Mix at the composition ratio shown and L/D is 22
Using a 40mmφ extruder, the resin was melt-extruded into strands at a resin temperature of 285°C, cooled, and then cut into 4mm lengths to form pellets. These were then melt-extruded in a rotary vacuum dryer at a vacuum of 1mmHg at 150°C. After drying for 5 hours, dried pellets having various composition ratios were obtained. These various pellets are made into Meiki Seisakusho SJ-40C.
Injection molding machine with resin temperature of 280℃ and injection pressure of 40Kg/cm ²
(gauge pressure), molding cycle of 50 seconds, direct gate conditions, and the linear speed and mold temperature during resin molding shown in Table 1, total length 137 mm,
Body outer diameter 26mm, body wall thickness 3mm, mouth thread outer diameter 28mm
A preform with a threaded bottom and a thickness of 1.5 mm was obtained. All of these bottomed preforms exhibited pearly surface gloss. Next, these bottomed preforms were placed in a biaxial stretch blow molding machine, and while rotating the bottomed preforms, the surface temperature was raised using a far infrared heater for 35 seconds.
Heat until the temperature reaches 120℃, then the surface temperature is 95℃
Stretching ratio and blow pressure such that the longitudinal stretching ratio is 1.4 times and the horizontal stretching ratio is 2.2 times
Biaxial stretch blow molding was performed at kg/cm ² to obtain a hollow container. The pearl property appearance evaluation results of the bottomed preform and the hollow container, the capacity measurement results of the hollow container as a measure of mold reproducibility during blow molding of the hollow container, and the measurement results of the falling strength of the hollow container were evaluated in the first test. Shown in the table. As a comparative example, the copolymerization ratio was outside the range of the present invention.
PMMA and PET of various [η] were mixed at the composition ratios shown in Table 2, and the pellets were formed into pellets under the same conditions as in the above example, and the same evaluation was conducted as a bottomed preform and a hollow container. Summer. These results are shown in Table 2.

【table】

【table】

[Table] Examples 20-21, Comparative Examples 11-12 Same as Examples 1-19 except that the linear speed and mold temperature of the various resin compositions shown in Table 3 were set to the conditions shown in Table 3. Full length injection molded under injection molding conditions.
137mm, body outer diameter 24mm, mouth thread outer diameter 28mm (thickness)
Threaded bottomed preforms having various body thicknesses of 1.5 mm) were obtained. Next, these bottomed preforms were prepared in Examples 1 to 1.
A hollow container was obtained by molding using the biaxial stretch blow molding machine shown in No. 19 under the same conditions. Evaluation results similar to those of Examples 1 to 19 are shown in Table 3. In addition, as a comparative example, a resin composition shown in Table 3 was injection molded under the same injection molding conditions as in Examples 1 to 19, except that the linear speed and mold temperature were set to the conditions shown in Table 3. Comparative Example 11 The total length is 137mm, the outer diameter of the body is 24mm,
Body thickness 0.3mm, mouth thread outer diameter 28mm (wall thickness 1.5mm)
Comparative example 12 has a total length of 137 mm for the preformed body with a threaded bottom.
mm, body outer diameter 50mm, body thickness 13mm, mouth thread outer diameter
A 52 mm (thickness: 10 mm) threaded bottomed preform was obtained. These were biaxially stretched and blow molded in the same manner as above, and the evaluation results are also shown in Table 3.

[Table] Examples 22 to 31, Comparative Examples 13 to 17 Methacrylic resin (PMMA) made by copolymerizing MMA with various acrylic esters (hereinafter abbreviated as AE) at the copolymerization ratio shown in Table 4 Viscosity [η]
PET having a particle diameter of 1.1 was blended in the composition ratio shown in Table 4, and dried pellets were obtained in the same manner as in Examples 1 to 19. Next, these various pellets are made into Nissei Plastic ASB-
Using a 150 hot parison type blow molding machine, the resin temperature was 275℃, the injection pressure was 80Kg/cm ² (gauge pressure), the molding cycle was 1 minute, the linear speed was 150mm/sec, and the mold temperature was 20℃, and the total length was 110mm. A threaded bottomed preform with a body outer diameter of 22 mm and a body wall thickness of 2.0 mm was obtained. These bottomed preforms were blow molded at 90°C to obtain a ribbed round bottle with a total length of 137 mm and an outer diameter of 56 mm. These evaluation results are shown in Table 4 together with the results of comparative examples.

【table】

【table】

Claims (1)

[Scope of Claims] 1. A thermoplastic polyester resin whose main repeating unit is ethylene terephthalate and whose intrinsic viscosity is 0.75 to 1.40, and methyl methacrylate, at least one kind of acrylic ester represented by the following formula CH ₂ =CHCOOR (in the formula R is an alkyl group having 1 to 8 carbon atoms) and a methacrylic resin copolymerized with 5 to 40% by weight of The thickness is 0.5 by injection molding at a speed of 10 mm/sec or higher and a mold temperature of 55°C or lower.
A method for manufacturing a polyester hollow container, which comprises blow molding after forming a preformed body with a bottom of ~10 mm.