JP4174701B2 - Multilayer polyester sheet and molded product thereof - Google Patents

Description

【００３６】
表中の数字は各成分の重量%を表す。また、タルクのみ、樹脂の総量に対する重量部として示した。
【００３７】
【表２】

【００３８】
表２より、実施例１〜４に記載の多層ポリエステル系シート成形品は、金型汚れを生じず、かつ優れた耐衝撃性を示していることがわかる。また成形時における離型性、型決まり性も良好であった。一方、比較例１〜３では、耐衝撃性および金型汚れの点で問題があることが明らかである。
【００３９】
【発明の効果】
以上特定組成のポリマーからなる本発明の多層ポリエステル系シートから得られた成形品は、表２からも明らかなように成形時の金型汚れを低減しかつ充分な耐衝撃性を有している。よって本発明の多層ポリエステル系シートは、耐熱性、耐衝撃性等の特性を要求されるトレーなどの成形品を得るのに適したものであり、産業界に寄与すること大である。[0001]
BACKGROUND OF THE INVENTION
The present invention is a polyester sheet suitable for obtaining molded articles such as trays that require characteristics such as heat resistance and impact resistance. Specifically, it has excellent crystallinity and container moldability and reduces mold contamination during molding. The multilayered polyester sheet and the molded product thereof.
[0002]
[Prior art]
With the widespread use of household microwave ovens and ovens, food trays that can withstand use at high temperatures are needed. In particular, trays for semi-cooked frozen foods must be able to withstand use not only at high temperature conditions during cooking but also at freezing conditions during storage, that is, at a wide temperature range of about -20 ° C to about 200 ° C. is there. Currently, as a food tray having the above characteristics, a crystallized resin tray obtained by crystallizing a polyester-based sheet mainly made of polyethylene terephthalate resin (hereinafter referred to as PET) at the time of container molding has been put into practical use.
[0003]
However, since polyester-based sheets made of PET require time for crystallization when thermoforming a container, there has been a problem that the molding cycle during container production is relatively long. Furthermore, although such a tray made of PET has sufficient heat resistance, it cannot be said to have sufficient impact resistance, and has a drawback that the container is severely damaged by impact.
[0004]
In order to solve the above problem, a polyester-based sheet made of a resin obtained by adding a small amount of polyolefin to PET (hereinafter referred to as C-PET) has been proposed. It is known that the C-PET sheet has improved crystallinity during thermoforming as compared with the PET sheet, and is relatively excellent in formability. It is also known that the impact resistance of a container obtained from a C-PET sheet is better than that of a container made of a PET sheet.
[0005]
However, even in a container made of C-PET, it cannot be said that the impact resistance at low temperature is sufficient, and the drawback that the container is partially broken when an impact is applied during movement at the freezing temperature has not been solved. Not in. In addition, with the recent changes in lifestyle, consumption of frozen and heated foods that can be easily cooked is increasing, and the need for heat-resistant containers with better impact resistance is increasing. It is.
[0006]
In addition, when this type of food tray is produced by sheet thermoforming, the amount of sheet sag during preheating is optimized, mold releasability is improved, mold dirt adhesion is reduced, and molding cycles Improvement of moldability such as shortening of the mold is also necessary, but in the above-mentioned C-PET, there is a problem that polyolefin adheres to the mold during molding, that is, mold contamination is remarkable, and an early solution is desired. .
[0007]
As a method for improving the above-mentioned drawbacks, a patent on a multilayer sheet using C-PET as a surface layer and PET-G which is an amorphous polyester as an inner layer, or C-PET using a polyethylene ionomer as a polyolefin has been filed. Has been.
[0008]
However, although the former multilayer sheet is excellent in impact resistance, it cannot solve the mold contamination during molding. In addition, the container made of the latter C-PET cannot be said to have sufficient impact resistance, and has the disadvantage that it has a strange odor during heating and heat setting, and also has the disadvantage of discoloration due to poor heat resistance. Has not reached.
[0009]
[Problems to be solved by the invention]
As described above, the current polyester-based sheet and a molded article made of the sheet cannot solve various problems in molding and use. Based on the above background, the present invention is a polyester sheet suitable for obtaining a molded article such as a tray which requires properties such as heat resistance and impact resistance, and more specifically, excellent in crystallinity and container moldability and molded. It is an object of the present invention to provide a polyester sheet with reduced mold contamination and a molded product thereof.
[0010]
[Means for Solving the Problems]
As a result of intensive studies in order to solve the above problems, the present inventors have found that the above problems can be solved by adopting a multilayer structure composed of a surface layer and an inner layer having a specific composition in a polyester-based sheet. It was found and reached the present invention.
[0011]
That is, the present invention is as follows.
1. Surface layer comprising 99% by weight or more of polyester resin having an intrinsic viscosity of 0.70 dL / g or more and 1% by weight or less of polyolefin resin, 92 to 99% by weight of polyester resin having an intrinsic viscosity of 0.70 dL / g or more, and polyolefin It has an inner layer made of a system resin 1-8 wt%, all part or of the polyolefin resin constituting the inner layer Ri modified polyolefin resin der, multilayer polyester sheet of the modified polyolefin resin is a glycidyl methacrylate copolymer .
2. 2. The multilayer polyester sheet according to 1 above, wherein an average dispersed particle size of the polyolefin resin in the inner layer portion of the multilayer polyester sheet is 3 μm or less.
3 . A molded article comprising the polyester sheet according to 1 or 2 above, wherein the surface layer has a crystallinity of 10 to 40%.
[0012]
The present invention is described in detail below. Examples of the polyester used in the multilayer polyester sheet in the present invention include polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate, polycyclohexylenedimethylene terephthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene naphthalate, liquid crystalline polyester, and the like. Examples of the polyester include those obtained by adding an arbitrary crystal nucleating agent to the polyester. Particularly preferable is PET in which a crystal nucleating agent is added from the viewpoint of crystallinity, moldability, heat-resistant temperature and price of the resin.
[0013]
The polyester used in the present invention has an intrinsic viscosity of 0.70 dL / g or more, preferably 0.80 dL / g or more. When the intrinsic viscosity is 0.70 dL / g or less, the obtained sheet and the molded product thereof are inferior in mechanical strength, and operation failure due to sheet sagging easily occurs in the sheet preheating process at the time of container molding, which is not preferable. .
[0014]
The polyester in the present invention may use other aromatic dicarboxylic acid, alicyclic dicarboxylic acid, or aliphatic dicarboxylic acid as a part of the acid component. Aromatic dicarboxylic acids include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, hydroxybenzoic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxy Examples include ethanedicarboxylic acid, 3,5-dicarboxybenzenesulfonic acid, and 5-sodium sulfoisophthalic acid. Examples of the alicyclic dicarboxylic acid include cyclohexane dicarboxylic acid and tetrahydrophthalic anhydride. Examples of the aliphatic dicarboxylic acid include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, and hydrogenated dimer acid. These are used within a range that does not significantly reduce the melting point and crystallinity of the resin, and the amount thereof is less than 20 mol%, preferably less than 10 mol% of the total acid component.
[0015]
In the polyester of the present invention, other types of glycols, that is, alkylene glycols having 1 to 25 carbon atoms, can be used as part of the glycol component. For example, diethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonane Examples thereof include diol, neopentyl glycol, dimethylol heptane, dimethylol pentane, tricyclodecane dimethanol, ethylene oxide derivatives of bisphenol X (X is A, S, F). These glycols are used in an appropriate combination depending on the balance of various properties, but since the premise is that the crystallinity of the main ester unit in the polymer is not hindered, the amount of copolymerization thereof is 20 mol% of the total glycol component. The following is desirable.
[0016]
The polyester in the present invention may contain a tri- or higher functional polycarboxylic acid or polyol component only in a small amount. For example, trimellitic anhydride, benzophenone tetracarboxylic acid, trimethylolpropane, glycerin, pyromellitic anhydride, pentaerythritol, 5-hydroxyisophthalic acid and the like can be used at 3 mol% or less.
[0017]
The polyester in the present invention can contain a difunctional polyether component only in a small amount. For example, PTMG, ethylene oxide modified PTMG, or the like can be used at 10% by weight or less. Moreover, 10 weight% or less can also be used for compounds, such as p-phenylphenol, benzyloxybenzoic acid, naphthalene monocarboxylic acid, and polyethylene glycol monomethylene ether.
[0018]
The amount of the polyolefin resin used for the surface layer of the multilayer polyester sheet in the present invention is required to be 1% by weight or less, and more preferably 0.5% by weight or less. It is not preferable that more than 1% by weight of the polyolefin resin is present in the surface layer because, for example, the polyolefin resin is transferred to the mold during vacuum molding or pressure molding, which may cause mold contamination.
[0019]
Examples of the polyolefin resin include high-density polyethylene, branched low-density polyethylene, linear low-density polyethylene, polypropylene, maleic acid-modified polyethylene, vinyl acetate-ethylene copolymer, ethyl acrylate-ethylene copolymer, and ethylene-propylene copolymer. Examples thereof include a polymer, a glycidyl methacrylate-ethylene copolymer, and a glycidyl methacrylate-ethyl acrylate-ethylene copolymer. These may be used alone or in combination of two or more.
[0020]
Any known crystal nucleating agent, for example, inorganic nucleating agents such as talc, kaolin and silica, and organic nucleating agents such as PBT oligomer, sodium benzoate and sodium stearate are added to the surface layer of the multilayer polyester sheet in the present invention. can do. The addition amount of the crystal nucleating agent is 0.01 to 5% by weight, and is appropriately set according to the kind of the nucleating agent. As the crystal nucleating agent having the effect of improving impact resistance, the above-mentioned polyolefin resins such as polyethylene and polypropylene are known, but these may be used in a range that does not cause mold contamination.
[0021]
As the polyolefin resin used in the inner layer of the multilayer polyester sheet of the present invention, for example, glycidyl methacrylate - ethylene copolymer, glycidyl methacrylate - include modified polyolefin resins such as ethylene copolymers - ethyl acrylate. In the present invention, from the viewpoint of improving the impact resistance of the inner layer, the glycidyl methacrylate copolymer and the low density polyethylene are used in combination, or the glycidyl methacrylate copolymer is used alone .
[0022]
The amount of the polyolefin resin added is 1 to 10% by weight, preferably 3 to 7% by weight, based on the total weight of the inner layer. If it is less than 1% by weight, the impact resistance improving effect is not sufficient, and if it is more than 10% by weight, an unpleasant odor peculiar to polyolefin resins is generated, which is not preferable.
[0023]
The melt flow rate (hereinafter referred to as MFR) of the polyolefin-based resin is 5 g / 10 min or less, preferably 3 g / 10 min or less, from the viewpoint of the impact resistance improving effect and the fine dispersibility in PET.
[0024]
The average dispersion particle diameter of the polyolefin resin is 3 μm or less, preferably 1.5 μm or less. When the average dispersed particle size is larger than 3 μm, the impact resistance of the molded product is inferior, which is not preferable.
[0025]
The crystallinity of the surface layer of the molded container or the like is 10 to 40%, preferably 20 to 35%. If the degree of crystallinity is less than 10%, sufficient heat resistance of the container cannot be obtained, and if it is more than 40%, it becomes an overcrystallized state and impact resistance is remarkably lowered.
[0026]
The multilayer polyester-based sheet of the present invention is usually composed of a surface layer (the outermost layer of a container when used as a container), an intermediate layer, and an inner layer (the innermost layer when used as a container). : Intermediate layer: Inner layer = 0.1: 9.8: 0.1 to 3: 4: 3 is preferable. The number of layers is usually three layers, but in addition, for example, five layers or seven layers may be used, and the total thickness ratio in this case is equivalent to the thickness ratio in the case of the three layers.
[0027]
The multilayer polyester sheet of the present invention is produced by a usual coextrusion method. Further, the sheet is processed into a container such as a tray by molding such as pressurization, vacuum, and compression.
[0028]
In each layer of the multilayer polyester sheet of the present invention, various polymers or additives can be blended depending on the purpose to obtain a composition. Examples of the polymer include polyamide polymers, polyester elastomers and other polyester polymers, polystyrene polymers, polyacrylic polymers, and the like. Additives include known hindered phenol-based, sulfur-based, phosphorus-based, amine-based antioxidants, hindered amine-based, triazole-based, benzophenone-based, benzoate-based, nickel-based, salicyl-based light stabilizers, antistatic agents, etc. Agents, lubricants, molecular modifiers such as peroxides, compounds having reactive groups such as epoxy compounds, isocyanate compounds, carbodiimide compounds, metal deactivators, organic and inorganic nucleating agents, neutralizing agents, control agents Acid agents, antibacterial agents, fluorescent whitening agents, fillers, flame retardants, flame retardant aids, organic and inorganic pigments, dyes, and the like can be added.
[0029]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in full detail, this invention is not limited to this. The main physical property values are measured as follows.
(1) Measurement was performed at a temperature of 30 ° C. using a mixed solvent of IV: phenol / tetrachloroethane = 60/40 (weight ratio).
[0030]
(2) Average dispersed particle diameter of polyolefin-based resin in the inner layer of the sheet: The produced sheet was cooled with liquid nitrogen and folded in a direction parallel to the pushing direction. After depositing gold on the sheet fragments, the fracture surface was observed with a scanning electron microscope, and the dispersion average particle diameter of the polyolefin resin in the inner layer of the sheet was measured.
[0031]
(3) Mold dirt: A vacuum-pneumatic molding machine TVP-33 manufactured by Sanwa Kogyo Co., Ltd. was used to perform vacuum molding using a mirror-finished mold (full capacity 320 cc) to obtain a container. The sheet was preheated at a heater output of 90%, and the mold temperature was 180 ° C. Molding was performed 300 times continuously, and the amount of polyolefin adhered to the mold surface was visually observed and evaluated.
[0032]
(4) Impact strength: When a 176 g weight (impact surface: hemisphere with a diameter of 12 mm) was dropped from a height of 50 cm using a DuPont drop weight impact tester in a 0 ° C. atmosphere using a tray container cut piece. Evaluation was made based on the number of cracks with respect to 15 test pieces.
[0033]
The polyester resin, polyolefin resin and modified polyolefin resin used are as follows.
PET: Toyobo Co., Ltd. IV = 1.00 g / dl PET resin Polyolefin resin: Nippon Polychem Co., Ltd. linear low density polyethylene Novatec LL (UF230)
Modified polyolefin resin: Bond First 2C and 7M manufactured by Sumitomo Chemical Co., Ltd.
(2C: ethylene-glycidyl methacrylate copolymer; 7M: ethylene-alkyl acrylate-glycidyl methacrylate copolymer)
[0034]
Examples 1-4 and Comparative Examples 1-3
Using each of the above resins, a 0.5 mm thick multilayer sheet was obtained with a homemade sheeting machine. The resin compositions of the sheet inner layer and the surface layer are summarized in Table 1 below. In addition, all the barrel temperatures at the time of sheet forming were 290 degreeC. Next, by using this sheet, a tray container having a full capacity of 320 cc was obtained with a vacuum pressure forming machine TVP-33 manufactured by Sanwa Kogyo Co., Ltd. The sheet was preheated at a heater output of 90%, and the mold temperature was 180 ° C. The molded container obtained from each sheet was evaluated for the average dispersed particle diameter of the polyolefin resin, mold contamination, and impact strength based on the evaluation method described above. The results are shown in Table 2.
[0035]
[Table 1]

[0036]
The numbers in the table represent the weight percent of each component. Moreover, only talc was shown as a weight part with respect to the total amount of resin.
[0037]
[Table 2]

[0038]
From Table 2, it can be seen that the multilayer polyester sheet molded products described in Examples 1 to 4 do not cause mold contamination and exhibit excellent impact resistance. Moreover, the mold release property and mold determination at the time of molding were also good. On the other hand, it is apparent that Comparative Examples 1 to 3 have problems in terms of impact resistance and mold contamination.
[0039]
【The invention's effect】
As can be seen from Table 2, the molded product obtained from the multilayer polyester sheet of the present invention comprising a polymer having a specific composition has reduced mold contamination during molding and has sufficient impact resistance. . Therefore, the multilayer polyester sheet of the present invention is suitable for obtaining molded articles such as trays that require characteristics such as heat resistance and impact resistance, and greatly contributes to the industrial world.

Claims (3)

Surface layer comprising 99% by weight or more of polyester resin having an intrinsic viscosity of 0.70 dL / g or more and 1% by weight or less of polyolefin resin, 92 to 99% by weight of polyester resin having an intrinsic viscosity of 0.70 dL / g or more, and polyolefin having at least an inner layer made of a system resin 1-8 wt%, all part or of the polyolefin resin constituting the inner layer Ri modified polyolefin resin der, multilayer polyester the modified polyolefin resin is a glycidyl methacrylate copolymer Sheet.  The multilayer polyester sheet according to claim 1, wherein an average dispersed particle diameter of the polyolefin resin in the inner layer portion of the multilayer polyester sheet is 3 µm or less. A molded article comprising the polyester-based sheet according to claim 1 or 2 , wherein the surface layer has a crystallinity of 10 to 40%.