JP2005171109A - Polyester resin for compression molding, manufacturing method of preform, preform and polyester container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin for compression molding which satisfies both of conveyablity to a compression molding machine and resin flowability on compression molding and has enhanced production efficiency, and an efficiently productive manufacturing method of a preform. <P>SOLUTION: The polyester resin for compression molding has surface tension at 280°C of 25-50 mN within an intrinsic viscosity (IV) range of 0.70-0.90 dL/g. The manufacturing method of the preform comprises supplying a melt resin mass composed of the polyester resin to a compression molding machine and compression molding the same. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a polyester resin for compression molding, and more specifically, a polyester resin that can satisfy both the transportability to a compression molding machine and the fluidity of the resin in compression molding, and a preform molded using this resin. The present invention relates to a polyester container and a method for producing a preform using the resin.

Stretch blow molded plastic containers, in particular biaxially stretched polyester containers, are now commonplace, and liquids such as liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc. due to their excellent transparency and moderate gas barrier properties. In addition to containers for foods and the like, they are widely used for carbonated drinks such as beer, cola and cider, and other drink containers such as fruit juice and mineral water.
When forming a biaxially stretched polyester container, a bottomed preform having a size considerably smaller than the final container and having an amorphous polyester is formed in advance by injection molding of a polyester resin, and the preform is brought to its stretching temperature. A method of preheating, stretching in the axial direction in the blow mold and blow-stretching in the circumferential direction is employed (for example, Patent Document 1).

As the shape of the bottomed preform, a mouth-and-neck portion corresponding to the mouth-and-neck portion of the container and a bottomed cylindrical portion to be stretch blow molded are generally used, and the shape as a whole is a test tube. The mouth / neck portion is formed with, for example, a sealing opening end or an engaging means with a lid. In addition, a gate portion that protrudes outward from the center of the bottom portion is always formed on the bottom portion because of the necessity of injection molding.
However, in general, in the manufacture of a preform by injection molding, the melt-plasticized resin is injected into the cavity through the nozzle, sprue, runner, and gate, so that the residence time of the resin in the injection molding machine is long. A long stay in a simple molding machine may cause deterioration of the resin. In particular, the polyester resin has a problem in that satisfactory mechanical strength cannot be obtained because the intrinsic viscosity and molecular weight decrease due to thermal decomposition.
Further, acetaldehyde is generated during the thermal decomposition of the polyester resin, and the acetaldehyde remaining in the polyester causes a decrease in the flavor retention of the polyester container.

  From such a viewpoint, it has already been proposed to produce a bottomed preform by compression molding of a resin. For example, Patent Document 2 discloses a female mold in which a molten resin mass extruded from an extruder is cut and held. A method for manufacturing a preform is described, which comprises supplying a male mold into the female mold and compressing the female mold into the female mold after being supplied into the female mold.

JP-A-4-154535 JP 2000-280248 A

However, in the production of a preform by compression molding, even if the above-mentioned whitening tendency of the gate portion is eliminated, the intrinsic viscosity (IV) is lowered during plasticization of the resin, and the molten resin mass is turned into a compression mold. There is a problem that the transportability of the paper is lowered.
That is, in the compression molding of the preform, it is necessary to transport the molten resin mass (drop) extruded from the extruder to the compression molding position, but a crystalline resin capable of stretching orientation such as a thermoplastic polyester resin is In general, the tendency to draw down is large, and when plasticization, that is, the decrease in intrinsic viscosity (IV) during melt kneading is large, drawdown occurs during drop molding, and it is difficult to accurately hold the molten resin mass Or, the molten resin lump may be brought into close contact with the conveying jig and cannot be supplied smoothly to the compression mold, and the conveying property of the molten resin lump is deteriorated. On the other hand, if the intrinsic viscosity (IV) of the molten resin mass is increased to eliminate the drawdown tendency, the transportability is improved, but the extrudability of the molten resin from the extruder and the generation of cutter marks due to the cutting of the molten resin Due to the damage of the preform due to the above, the compression moldability is lowered due to the decrease in the fluidity of the resin.

Accordingly, an object of the present invention is to provide a polyester resin for compression molding in which the above-described problems are solved and production efficiency can be improved, and a preform production method with high production efficiency.
Another object of the present invention is to provide a preform having excellent appearance characteristics and a polyester container formed by stretching the preform.

According to the present invention, there is provided a polyester resin for compression molding characterized by having an intrinsic viscosity (IV) in the range of 0.70 to 0.90 dL / g and a surface tension at a temperature of 280 ° C. of 25 to 50 mN. .
According to the present invention, in the method of supplying a molten resin lump made of a polyester resin to a compression mold and compressing and molding the molten resin lump, the molten resin lump has an intrinsic viscosity (IV) of 0. There is provided a method for producing a preform, comprising a polyester resin having a surface tension of 25 to 50 mN at a temperature of 280 ° C. at .70 to 0.90 dL / g.
According to the present invention, there is further provided a preform produced by the above production method and a polyester container formed by stretching the preform.

According to the polyester resin for compression molding of the present invention, the occurrence of resin drawdown during melt extrusion can be effectively suppressed, and adhesion of the molten resin mass to the conveying jig can be effectively prevented, leading to a compression molding machine. It is possible to improve the transportability of the molten resin lump (drop), and it is possible to form the preform by compression molding with high productivity. Further, the cutter mark is not formed when the molten resin extruded from the extruder is cut, and the preform can be prevented from being damaged. Furthermore, since the fluidity of the molten resin mass is also excellent, the compression moldability (shapeability) is also excellent.
Further, the preform formed by compression-molding the above-mentioned polyester resin for compression molding of the present invention has an advantage that there is no fluid orientation strain at the bottom, and that no gate part or other trimming operation is required. Further, even if the polyester container formed by stretching the preform is a multilayer container, there is an advantage that there is no disorder in the layer structure at the center of the bottom and that the appearance characteristics and impact resistance of the bottom are excellent.

  In the present invention, when the molten polyester resin is extruded from the extruder, the molten resin lump tends to draw down and the molten resin lump is in close contact with the conveying jig, making it difficult to supply to the compression molding machine smoothly. The polyester resin used for compression molding was found to be caused by the surface characteristics of the molten resin mass, and the surface tension at an intrinsic viscosity (IV) of 0.70 to 0.90 dL / g and a temperature of 280 ° C. was 25 to 50 mN, particularly 30. By using a material having a viscosity of 45 mN, problems such as a tendency to draw down the molten resin mass can be solved.

Further, in the present invention, the molten resin lump surface supplied to the compression molding machine has a predetermined surface tension, thereby suppressing the occurrence of drawdown and the close contact with the conveying jig, thereby conveying the molten resin lump. In addition to improving productivity, it is also possible to suppress the formation of cutter marks when the molten resin extruded from the extruder is cut, thereby preventing the preform from being damaged. Furthermore, since it has a certain intrinsic viscosity, it is possible to exhibit an effect that it is excellent in compression moldability because it is excellent in fluidity of the molten resin mass.
In the present invention, the intrinsic viscosity of 0.70 to 0.90 dL / g and the temperature of 280 ° C. are used as a standard, in order to form a preform by compression molding, it is necessary to have an intrinsic viscosity of at least the above range. In addition, the temperature of 280 ° C. is based on a temperature within a general temperature range of the molten resin to be melt-extruded.

Such operational effects of the present invention are also apparent from the results of Examples described later. That is, a polyester resin (Comparative Example 1) having an intrinsic viscosity within the above range but a surface tension of less than 25 mN, or a polyester resin having a surface tension within the above range but having an intrinsic viscosity less than the above range (Comparative Example) When compression molding is performed using 2), drawdown occurs during melt extrusion, and it cannot be supplied efficiently to the compression molding machine in close contact with the transport jig, resulting in poor transportability of the molten resin mass. I understand that. In addition, the intrinsic viscosity is in the upper range but the surface tension is greater than 50 mN (Comparative Example 3), or the surface tension is in the above range but the intrinsic viscosity is greater than the above range (Comparative Example 4). When the compression molding is performed using the above, the fluidity of the resin is inferior when the compression molding is performed, and the preform is scratched due to the cutter mark, and the compression molding property is poor.
On the other hand, when compression molding is performed using a polyester resin (Examples 1 to 3) whose intrinsic viscosity and surface tension are within the above ranges, drawdown is suppressed and the molten resin lump is reliably transported. It is understood that while being held by the tool and supplied into the compression mold, it is excellent in fluidity and compression moldability, and further, the cutter mark is not generated and the appearance characteristics of the polyester container are also excellent.

(Polyester resin)
The polyester resin used in the present invention is from the conventionally known dicarboxylic acid component and diol component except that the intrinsic viscosity (IV) is 0.70 to 0.90 dL / g and the surface tension at a temperature of 280 ° C. is 25 to 50 mN. A polyester resin can be used.

  As the dicarboxylic acid component, 50% or more, particularly 80% of the dicarboxylic acid component is preferably terephthalic acid from the viewpoint of mechanical properties and thermal properties, but it is of course possible to contain a carboxylic acid component other than terephthalic acid. Examples of carboxylic acid components other than terephthalic acid include isophthalic acid, naphthalenedicarboxylic acid, p-β-oxyethoxybenzoic acid, biphenyl-4,4′-dicarboxylic acid, diphenoxyethane-4,4′-dicarboxylic acid, 5- Examples thereof include sodium sulfoisophthalic acid, hexahydroterephthalic acid, adipic acid, sebacic acid and the like.

  As the diol component, 50% or more, particularly 80% or more of the diol component is preferably ethylene glycol in view of mechanical properties and thermal properties. As diol components other than ethylene glycol, 1,4-butanediol, Examples thereof include propylene glycol, neopentyl glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol, cyclohexane dimethanol, an ethylene oxide adduct of bisphenol A, glycerol, and trimethylolpropane.

  The polyfunctional component is a tribasic or higher polybasic acid or polyhydric alcohol, trimellitic acid, pyromellitic acid, hemimellitic acid, 1,1,2,2-ethanetetracarboxylic acid, 1,1,2- Polybasic acids such as ethanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, biphenyl-3,4,3 ′, 4′-tetracarboxylic acid, Polyhydric alcohols such as pentaerythritol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, sorbitol, 1,1,4,4-tetrakis (hydroxymethyl) cyclohexane are exemplified.

  The polyester resin for compression molding of the present invention has an intrinsic viscosity necessary for molding a preform by compression molding, that is, 0.70 to 0.90 dL / g, particularly 0.75 to 0.85 dL / g (weight ratio 1). 1) (measured at 30 ° C. using a 1: phenol / tetrachloroethane mixed solvent). As described above, when the intrinsic viscosity is not in the above range, satisfactory transportability and compression moldability of the molten resin mass cannot be obtained even if the surface tension is in the above range.

  In order to adjust the surface tension of the polyester resin for compression molding of the present invention at an intrinsic viscosity (IV) of 0.70 to 0.90 dL / g and a temperature of 280 ° C. within a range of 25 to 50 mN, particularly 30 to 45 mN, It can adjust by changing various conditions, such as a composition of a polyester resin, such as a polymerization component and its compounding quantity, the amount of oligomers contained, or melt viscosity.

Furthermore, the polyester resin preferably has a melting point (Tm) of less than 265 ° C., particularly 220 to 255 ° C., in order to satisfy the heat resistance and processability of the preform or polyester container. The glass transition point is preferably 30 ° C. or higher, particularly 50 to 120 ° C.
The polyester resin of the present invention contains known compounding agents for resins such as colorants, antioxidants, stabilizers, various antistatic agents, mold release agents, lubricants, nucleating agents, etc. It can mix | blend according to a well-known prescription in the range which is not.

(preform)
The preform of the present invention is obtained by compression-molding the above-mentioned compression-molding polyester resin, but it is made of the above-mentioned compression-molding polyester resin as well as a single layer composed only of the above-mentioned compression-molding polyester resin. A multilayer preform having a layer made of another thermoplastic resin in the layer may be used.
As the thermoplastic resin other than the polyester resin, any resin can be used as long as it is a resin that can be stretch blow molded and thermally crystallized, and is not limited thereto. However, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene- Examples thereof include olefin resins such as vinyl alcohol copolymers and cyclic olefin polymers, and polyamide resins such as xylylene group-containing polyamide. In addition, oxygen-absorbing gas barrier resin compositions containing diene compounds and transition metal catalysts in polyamides containing xylylene groups, recycled polyesters (PCR (resin that recycles used bottles), SCRs (generated in production plants) Resin) or a mixture thereof) can also be used. These recycled polyester resins preferably have an intrinsic viscosity (IV) measured by the method described above in the range of 0.65 to 0.75 dL / g.

The recycled polyester can be used alone or as a blend with virgin polyester. When the recycled polyester has a reduced intrinsic viscosity, it is preferably used by blending with the virgin polyester. In this case, the ratio of the recycled polyester: virgin polyester is 1: 5 to 5: 1. Preferably there is.
Moreover, in order to adhere | attach an inner layer or an outer layer, and an intermediate | middle layer, adhesive resin can also be interposed. As the adhesive resin, an acid-modified olefin resin obtained by graft polymerization of maleic acid or the like, an amorphous polyester resin, a polyamide resin, or the like can be used.
Moreover, various additives for resin can be mix | blended with thermoplastic resins other than the said polyester resin similarly to the said polyester resin for compression molding.

Although the layer structure of the multilayer preform of the present invention is not limited to this, the following can be exemplified. The following abbreviations in the multilayer structure are: PET: polyester resin for compression molding of the present invention, GBR: gas barrier resin, PCR: recycled polyester resin, ADR: adhesive resin, OAR: oxygen-absorbing resin composition, COC : Cyclic olefin copolymer.
Three-layer structure: PET / GBR / PET, PET / PCR / PET
PET / (PET + PCR) / PET
Four-layer structure: PET / GBR / PCR / PET,
PET / GBR / OAR / PET,
PET / GBR / COC / PET
Five-layer structure: PET / ADR / GBR / ADR / PET
PET / ADR / OAR / ADR / PET
PET / GBR / PCR / GBR / PET
PET / ADR / (GBR + OAR) / ADR / PET
Six-layer structure: PET / ADR / GBR / AR / PCR / PET
PET / ADR / OAR / ADR / PCR / PET
Seven-layer structure: PET / PCR / ADR / GBR / ADR / PCR / PET
PET / ADR / GBR / ADR / OAR / ADR / PET

(Preform molding)
As described above, the preform of the present invention can be molded by a conventionally known compression molding method using the above-described compression molding polyester resin.
In compression molding, since the residence time of the resin is short, there is little thermal deterioration of the resin as in injection molding, so that a general-purpose resin can also be used. In addition, the gate part that causes whitening of the bottom is not formed at the bottom as in the case of injection molding, and the flow orientation of the resin hardly occurs at the bottom of the preform, and the residual strain due to the fluid orientation occurs at the bottom. Therefore, there is an advantage that the physical properties of the molded product are less affected.

In other words, the melt of the polyester resin for compression molding according to the present invention is continuously extruded by an extruder, and the melt is cut to produce a molten resin lump (drop) which is a preform for a preform in a molten state. Then, this molten resin mass is put into a cavity mold of a compression molding machine, and this is compression molded with a core mold. At this time, as described above, the molten resin lump has an intrinsic viscosity (IV) in the range of 0.70 to 0.90 dL / g and a surface tension at a temperature of 280 ° C. in the range of 25 to 50 mN. And is important in terms of liquidity.
Further, when a large number of compression molding dies are arranged circumferentially on the rotating turret, the preform can be molded with high efficiency in an intermittent but nearly continuous state.

  In the preform production method of the present invention, the melt extrusion temperature of the molten polyester resin is preferably in the range of Tm + 5 ° C. to Tm + 40 ° C., particularly Tm + 10 ° C. to Tm + 30 ° C., based on the melting point (Tm) of the polyester resin. At a temperature lower than the above temperature, the shear rate becomes too high, and it may be difficult to form a uniform melt extrudate. On the other hand, at a temperature higher than the above range, the degree of thermal degradation of the resin increases. Or the drawdown becomes too large, and it becomes difficult to form a preform having the above-mentioned characteristics.

  FIG. 1 is an explanatory view showing a compression molding apparatus used when a multilayer preform is molded using the polyester resin for compression molding according to the present invention. The compression molding apparatus generally indicated by 1 is for compression molding according to the present invention. A resin A for inner and outer layers made of polyester resin is continuously supplied from the main extruder 2, and an intermediate layer resin B such as a gas barrier resin is intermittently supplied from the sub-extruder 3, The molten resin 7 is melt-extruded from the nozzle 5 provided below the multilayer die 4 so that the resin A encloses the resin B, and the composite molten resin 7 extruded by the cutting means 6 movable in the horizontal direction is used as the intermediate layer. Cut to a predetermined dimension at the part where no. The cut composite molten resin lump 8 is conveyed into a female mold 9 of a compression molding apparatus composed of a female mold 9 and a male mold 10 immediately after cutting, sandwiched between jigs. The composite molten resin mass 8 in the female mold 9 is compression-molded by the male mold 10 to form a multilayer preform in which the intermediate layer is sealed with the inner layer and the outer layer.

  FIG. 2 is a cross-sectional view of an example of a multilayer preform among the preforms of the present invention. The multi-layer preform indicated as a whole by 20 consists of a mouth-and-neck part 21, a trunk part 22 and a bottom part 23. In the specific example shown in the figure, the preform is formed by compression molding having no gate portion at the bottom, and the portion excluding the end portion 21a of the mouth and neck portion 21 is the same as the three layers of the inner layer 24, the intermediate layer 25 and the outer layer 26. It has a structure.

(Polyester container)
The polyester container of the present invention can be obtained by stretching the preform.
In the stretch blow molding, the preform of the present invention is heated to a stretching temperature, the preform is stretched in the axial direction, and biaxial stretch blow molding is performed in the circumferential direction to produce a biaxially stretched container.
The preform molding and the stretch blow molding can be applied to a hot parison system in which stretch blow molding is performed without completely cooling the preform, in addition to the cold parison system. Prior to stretching blow, if necessary, the preform is preheated to an appropriate stretching temperature by means of hot air, an infrared heater, high frequency induction heating or the like. In the case of polyester, the temperature range is 85 to 120 ° C., particularly 95 to 110 ° C.

The preform is supplied into a publicly known stretch blow molding machine, set in a mold, stretched in the axial direction by pushing a stretching rod, and stretched in the circumferential direction by blowing a fluid. In general, the mold temperature is preferably in the range of room temperature to 190 ° C. However, as described later, when heat setting is performed by the one mold method, the mold temperature is preferably set to 120 to 180 ° C.
The draw ratio in the final polyester container is suitably 1.5 to 25 times in terms of area magnification. Among these, the axial draw ratio is 1.2 to 6 times, and the circumferential draw ratio is 1.2 to 4.5. It is preferable to double.

The polyester container of the present invention can be heat-set by a means known per se. The heat setting can be performed by a one-mold method performed in a blow molding die, or can be performed by a two-mold method performed in a heat fixing die separate from the blow molding die. The temperature for heat setting is suitably in the range of 120 to 180 ° C.
As another stretch blow molding method, as illustrated in Japanese Patent No. 29178851 of the present applicant, a preform is subjected to primary blow molding having a size larger than that of a final molded product using a primary blow mold. A two-stage blow molding method may be employed in which the primary blow molded body is heated and shrunk, and then stretch blow molding is performed using a secondary blow mold to obtain a final molded product.

  An example of the multilayer structure of the polyester container of the present invention is shown in FIG. In FIG. 3, the biaxially stretched container generally indicated by 40 has a bottle shape and is composed of a mouth part 41, a body part 42 and a bottom part 43. The body part 42 and the bottom part 43 are composed of an inner layer 44a and an outer layer 44b. It consists of the intermediate | middle layer 45 enclosed in. The mouth portion 41 is formed of only the inner and outer layer resins as in the multilayer preform described above.

1. Measurement of surface tension Molten resin (drop) was extruded by a well-known pendant drop method, and the surface tension after being left in air at 280 ° C. for 20 minutes was measured.

[Example 1]
Homopolyethylene terephthalate having an intrinsic viscosity (IV) of 0.71 dL / g and a surface tension of 27 mN was supplied to an extruder hopper, extruded under conditions of a die temperature of 270 ° C. and a resin pressure of 70 kgf / cm ² , and cut into a molten resin lump. . The molten resin mass was conveyed into a compression mold at 20 ° C. and compression molded under the condition of a clamping pressure of 100 kgf / cm ² to prepare a single layer preform. It was possible to transport in a state where the deformation of the molten resin mass due to drawdown was satisfactorily suppressed, and the shapeability during compression was also good.

[Example 2]
Molding was performed in the same manner as in Example 1 except that homopolyethylene terephthalate having an intrinsic viscosity (IV) of 0.78 dL / g and a surface tension of 32 mN was used. It was possible to transport in a state where the deformation of the molten resin mass due to drawdown was satisfactorily suppressed, and the shapeability during compression was also good.

[Example 3]
Molding was carried out in the same manner as in Example 1 except that copolymerized polyethylene terephthalate containing 0.1 mol% of trimellitic acid as a polyfunctional component, having an intrinsic viscosity (IV) of 0.89 dL / g and a surface tension of 48 mN was used. went. It was possible to transport in a state where the deformation of the molten resin mass due to drawdown was satisfactorily suppressed, and the shapeability during compression was also good.

[Comparative Example 1]
Molding was performed in the same manner as in Example 1 except that copolymerized polyethylene terephthalate containing 8 mol% of isophthalic acid as a copolymerization component, having an intrinsic viscosity (IV) of 0.71 dL / g and a surface tension of 21 mN was used. As a result, the formability was good, but the conveyance was unstable due to deformation of the molten resin mass due to drawdown.

[Comparative Example 2]
Molding was performed in the same manner as in Example 1 except that copolymerized polyethylene terephthalate containing 0.05 mol% of trimellitic acid as the polyfunctional component, having an intrinsic viscosity (IV) of 0.67 dL / g and a surface tension of 27 mN was used. went. As a result, the formability was good, but the conveyance was unstable due to deformation of the molten resin mass due to drawdown.

[Comparative Example 3]
Molding was performed in the same manner as in Example 1 except that copolymerized polyethylene terephthalate containing 0.4 mol% of trimellitic acid as a polyfunctional component, having an intrinsic viscosity (IV) of 0.88 dL / g and a surface tension of 55 mN was used. went. As a result, conveyance of the molten resin mass was stable, but it was difficult to form and a good preform could not be formed.

[Comparative Example 4]
Molding was performed in the same manner as in Example 1 except that homopolyethylene terephthalate having an intrinsic viscosity (IV) of 0.98 dL / g and a surface tension of 49 mN was used. As a result, conveyance of the molten resin mass was stable, but it was difficult to form and a good preform could not be formed.

  The results of Examples and Comparative Examples are shown in Table 1 above.

It is a figure which shows an example of the compression molding machine used for shaping | molding of the preform of this invention. It is a figure which shows an example of the preform of this invention. It is a figure which shows an example of the polyester container of this invention.

Claims (4)

  A polyester resin for compression molding having an intrinsic viscosity (IV) of 0.70 to 0.90 dL / g and a surface tension at a temperature of 280 ° C. of 25 to 50 mN.   In the method of supplying a molten resin lump made of polyester resin to a compression mold and compression-molding it to produce a preform, the molten resin lump has an intrinsic viscosity (IV) of 0.70 to 0.90 dL / g. A preform manufacturing method comprising a polyester resin having a surface tension of 25 to 50 mN at a temperature of 280 ° C.   A preform manufactured by the manufacturing method according to claim 2.   A polyester container, wherein the preform according to claim 3 is stretch-molded.

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