JP2008006626A - Multilayer preform made of saturated polyester resin and multilayer bottle formed from the preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester preform excellent in transparency and surface slidability and a hollow molding. <P>SOLUTION: The multilayer preform made of a saturated polyester resin is formed from a saturated polyester resin layer having at least two layers including a skin layer and a core layer. The saturated polyester resin forming the skin layer contains inert particles with a mean particle size of 5 μm or below. A multilayer saturated polyester resin bottle is obtained by extension-molding the preform. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a polyester preform and a hollow molded body obtained by molding the preform.

A hollow molded body made of a saturated polyester resin typified by polyethylene terephthalate (hereinafter sometimes abbreviated as PET) is widely used for containers such as beverages.

  The hollow molded body as a beverage container is required to be transparent in view of the contents visibility and appearance. Further, in order to prevent the surfaces of the hollow molded bodies, in particular, the square hollow molded bodies from adhering to each other and falling down in the transporting process or the like, it is also required that the surface slipperiness is moderate.

  However, the actual situation is that a polyethylene terephthalate hollow molded article having both transparency and slipperiness at a high level has not been obtained.

JP-A-5-17598

The present invention has been made in view of the above problems,
It is an object of the present invention to provide a preform made of a saturated polyester resin having excellent transparency and surface slipperiness, and a molded product obtained by hollow blow molding the preform.

  The present inventor solves the above problems with a preform and a hollow molded body having at least two layers and containing inert particles having an average particle diameter of 5 μm or less in a polyester resin forming a skin layer (surface layer). The inventors have found that this is possible and have reached the present invention.

That is, the gist of the present invention is as follows.
(1) A saturated polyester resin multilayer preform formed from at least two different saturated polyester resin layers, and the saturated polyester resin forming the skin layer contains inert particles having an average particle diameter of 5 μm or less. A multilayer preform made of a saturated polyester resin, characterized by

(2) The present invention also relates to a saturated polyester resin multilayer bottle obtained by stretching the saturated polyester resin multilayer preform described in (1).

(3) The saturated polyester resin multilayer bottle described in (2), wherein the coefficient of static friction between the bottles is less than 1.00 and the bottle Haze is 7.0 or less.

According to the present invention, it is possible to provide a polyester preform and a hollow molded body which are excellent in transparency and excellent in surface sliding.

Hereinafter, the present invention will be described in detail.
[Saturated polyester]
As general-purpose saturated polyester resins used in the present invention, the following saturated polyester resins are used.
Polyethylene terephthalate obtained from terephthalic acid or an ester-forming derivative thereof and ethylene glycol or an ester-forming derivative thereof is preferably used. Examples of ester-forming derivatives of dicarboxylic acids include esters with monohydric alcohols such as dimethyl terephthalate and acid anhydrides. Examples of the ester-forming derivative of glycol include esters with monovalent carboxylic acids such as ethylene glycol diacetate.

As the aromatic dicarboxylic acid, besides terephthalic acid, phthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 4,4 ′ -Sulphone bisbenzoic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-sulfide bisbenzoic acid, 4,4'-oxybisbenzoic acid and the like can be used. These can be used alone or in combination of two or more.
The total amount of dicarboxylic acid is preferably 100 mol%, and preferably 80 mol% or more, and more preferably 90 mol% or more, with terephthalic acid as a main component.

Further, in the present invention, aromatic dicarboxylic acid, oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid and other aliphatic dicarboxylic acids, cyclohexane Alicyclic dicarboxylic acids such as dicarboxylic acids can be used as copolymerization components.

The main component of the diol is ethylene glycol, which is preferably 90 mol% or more, more preferably 95 mol% or more in all diol units, and other examples include, for example, 1,2-propanediol, 1,3 -Propanediol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, dodecamethylene glycol, triethylene glycol, tetraethylene glycol and the like can be used. In addition to ethylene glycol, these can be used alone or in combination of two or more.
Moreover, as diol components other than ethylene glycol, together with the above aliphatic diols, alicyclic diols such as cyclohexanedimethanol, 1,3-bis (2-hydroxyethoxy) benzene, 1,4-bis (2-hydroxy) Diols containing aromatic groups such as ethoxy) benzene, bis [4- (2-hydroxyethoxy) phenyl] sulfone, 2,2-bis (4-β-hydroxyethoxyphenyl) propane, bisphenols, hydroquinone, resorcin, etc. Can also be used.

  Furthermore, in the present invention, polyvalent carboxylic acids such as ethanetricarboxylic acid, propanetricarboxylic acid, pyromellitic acid, trimellitic acid, trimesic acid, 3,4,3 ′, 4′-biphenyltetracarboxylic acid, glycerin, diglycerin, (Trishydroxymethyl) methane, 1,1,1,-(trishydroxymethyl) ethane, 1,1,1,-(trishydroxymethyl) propane, pentaerythritol, dipentaerythritol, sorbitol, glucose, lactose, galactose, Polyhydric alcohols such as fructose, saccharose, 1,3,5-trishydroxyethoxyisocyanurate, glycolic acid, lactic acid, 4-hydroxy-n-butyric acid, 2-hydroxyisobutyric acid, 5-hydroxy-n-valeric acid, 3-hydroxypropionic acid, citric acid A unit derived from a polyfunctional compound such as hydroxycarboxylic acids such as malic acid, tartaric acid and p-hydroxybenzoic acid is contained as a copolymer component in a small amount, for example, 2 mol% or less with respect to 100 mol% of dicarboxylic acid units. May be.

The polyethylene terephthalate according to the present invention is produced by producing a low-order condensate from terephthalic acid or an ester-forming derivative thereof and ethylene glycol or an ester-forming derivative thereof, followed by polycondensation.

A low-order condensate (ester low polymer) is obtained by an esterification reaction of the terephthalic acid and ethylene glycol. The number average molecular weight of this low-order condensate is about 500 to 5,000. The esterification reaction is preferably carried out using an apparatus in which two or more reactors are connected in series while removing water generated by the reaction from the system using a rectification column under conditions where the diol is refluxed. . An esterification process can be performed by the method shown, for example in Unexamined-Japanese-Patent No. 2004-107382. The esterification reaction can be performed in the absence of a catalyst, but may be performed in the presence of a catalyst such as a germanium compound, an antimony compound, a titanium compound, or an aluminum compound.
Furthermore, in order to keep the amount of diethylene glycol in polyethylene terephthalate at a low level, tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine, tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, hydroxylated Quaternary ammonium such as trimethylbenzylammonium and basic compounds such as lithium carbonate, sodium carbonate, potassium carbonate and sodium acetate can also be added.

(Liquid phase polycondensation process)
The low-order condensate obtained in the esterification step is subjected to liquid phase polycondensation by heating under reduced pressure to a temperature not lower than the melting point of polyethylene terephthalate (usually 250 to 290 ° C.). This polycondensation reaction is desirably performed while distilling off unreacted ethylene glycol to the outside of the reaction system. The polycondensation reaction may be performed in one stage or may be performed in a plurality of stages. In the case of carrying out in a plurality of stages, the polycondensation reaction conditions are such that the first stage polycondensation reaction temperature is usually 250 to 290 ° C., preferably 260 to 280 ° C., and the pressure is usually 500 to 20 Torr. Is 200 to 30 Torr, and the temperature of the final polycondensation reaction is usually 260 to 300 ° C., preferably 270 to 295 ° C., and the pressure is usually 10 to 0.1 Torr, preferably 5 to 0.2 Torr. . The liquid phase polycondensation step can be performed, for example, by the method described in JP-A No. 2004-107382.

From the viewpoint of productivity, the polycondensation reaction is preferably polycondensed in the presence of a catalyst such as a germanium compound, an antimony compound, a titanium compound, or an aluminum compound. As these catalysts, known compounds can be used. These may be used alone or in combination. An alkali metal or alkaline earth metal compound can also be used in combination.
The polycondensation catalyst is used in an amount of 0.002 to 0.2 mol%, preferably 0.003 to 0.1 mol% in terms of metal atom, based on the dicarboxylic acid component in the low-order condensate. preferable.

Examples of germanium compounds include germanium dioxide, germanium tetroxide, germanium hydroxide, germanium oxalate, germanium tetraethoxide, germanium tetra-n-butoxide, germanium chloride, germanium glycoxide and the like.
Examples of the antimony compound include antimony trioxide, antimony pentoxide, antimony acetate, antimony glycoxide, antimony triethoxide, antimony trimethoxide, and the like.
Examples of titanium compounds include titanium alkoxides such as titanium tetra-n-butoxide, titanium tetraisopropoxide, titanium glycoxide, titanium halides such as titanium chloride, titanium acetylacetonate, titanium hydroxide, titanium oxalate, and potassium potassium oxalate. Etc.
Examples of the aluminum compound include aluminum formate, aluminum acetate, basic aluminum acetate, aluminum oxalate, aluminum chloride, aluminum hydroxide, aluminum acetylacetonate and the like.

It is preferable to add a phosphorus compound in addition to the polycondensation catalyst. The phosphorus compound added here is trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, mono Examples thereof include phosphoric esters such as butyl phosphate and dioctyl phosphate; phosphorous esters such as triphenyl phosphite, trisdodecyl phosphite and trisnonylphenyl phosphite, and phosphorus compounds such as phosphoric acid and polyphosphoric acid.
The addition amount of these phosphorus compounds is 0.001 to 0.2 mol%, preferably 0.002 to 0.1 mol% in terms of phosphorus atoms in the phosphorus compound with respect to the dicarboxylic acid. When the amount of the phosphorus compound is larger than this, the productivity of the polyethylene terephthalate resin may be impaired. When the amount of the phosphorus compound is less than this, the thermal stability of polyethylene terephthalate is lowered, and the resin may be yellowish.

(Pre-crystallization process)
The polyethylene terephthalate obtained by the liquid phase polycondensation step is usually formed into a granular shape and a chip shape, and further subjected to solid phase polycondensation if desired. At this time, in order to prevent fusion / adhesion between the chips, preliminary crystallization may be performed by heating to a temperature lower than that in the case of performing solid phase polycondensation in advance.
Such a precrystallization step can be performed by heating granular polyethylene terephthalate in a dry state to a temperature of usually 120 to 200 ° C., preferably 130 to 180 ° C. for 1 minute to 4 hours. Such precrystallization can also be performed by heating granular polyethylene terephthalate at a temperature of 120 to 200 ° C. for 1 minute or more in a steam atmosphere, a steam-containing inert gas atmosphere, or a steam-containing air atmosphere. .
Details of the precrystallization step are described in JP-A-10-139873.

(Solid phase polycondensation process)
The polyethylene terephthalate obtained in this liquid phase polycondensation step can further increase the degree of polymerization by the solid phase polycondensation step. The solid phase polycondensation step can be performed, for example, by the method described in JP-A No. 2004-107382.
In the solid phase polycondensation step, the temperature is 190 to 240 ° C., preferably 195 to 235 ° C., the pressure is 0.2 to 0.001 MPa (1 kg / cm 2 G to 10 Torr), preferably normal pressure to 0.01 MPa ( 100 Torr) under an inert gas atmosphere such as nitrogen, argon or carbon dioxide. Nitrogen gas is desirable as the inert gas used.

  The intrinsic viscosity of the thus obtained granular polyethylene terephthalate is usually 0.60 to 1.00 dl / g, preferably 0.70 to 0.90 dl / g. The amount of cyclic trimer (CT) composed of terephthalic acid and ethylene glycol contained in the resin after the solid phase polycondensation is 0.55% by weight or less, preferably 0.45% by weight or less, more preferably 0.8. It is desirable that it is 35% by weight or less.

The polyethylene terephthalate thus produced may contain a nucleating agent in order to control the crystallization rate. As the nucleating agent, conventionally known nucleating agents can be used, but it is preferable to use an organic nucleating agent because the transparency of the molded article is not deteriorated. Examples of the organic nucleating agent include polyolefin, polyamide, polyacetal and the like.
Addition method of organic nucleating agent is a method of adding to raw material, a method of adding in any step up to liquid phase polycondensation, and adding granular polyethylene terephthalate and nucleating agent in contact in any step after liquid phase polycondensation And a method of adding a master batch pellet containing an organic nucleating agent at a high concentration.

The polyethylene terephthalate produced in this way may be added with conventionally known additives, for example, colorants such as stabilizers, mold release agents, antistatic agents, dispersants, dyes and the like. These additives may be added at any stage during the production of polyethylene terephthalate, or may be added by a master batch before molding.
Accordingly, the above additives may be contained at a uniform concentration inside the particles of granular polyethylene terephthalate, or may be concentrated and contained in the vicinity of the particle surface of granular polyethylene terephthalate. Some particles of polyethylene terephthalate may be contained at a higher concentration than other particles.

The polyester preform of the present invention and the hollow molded body obtained by molding the preform have at least two layers of a skin layer and a core layer. Further, a molded body having three or more layers provided with gas barrier layers may be used.
The skin layer means an outer layer of a preform or a hollow molded body, and the core layer also means an inner layer.

The thickness of the preform is usually 2 mm to 6 mm, preferably 2 to 5 mm, and the ratio of the skin layer to the total thickness can be in the range of 1 to 99%, but the range of 5 to 50% It is preferable that it exists in. When the ratio of the skin layer is within this range, it is preferable in terms of improving slipperiness without impairing transparency.
The average body thickness of the hollow molded body is in the range of 0.2 mm to 0.6 mm.

(Skin Layer) As the skin layer, a polyester resin containing inert particles having the property of improving slipperiness is used.

(Core layer) As the core layer, a polyester resin having properties excellent in transparency and economy is desirable, and it is preferable to use a normal polyester containing no inert particles.

(Inert particles)
The skin layer contains inert particles having an average particle size of 5 μm or less. The average particle size is preferably 0.5 to 5 μm, more preferably 1 to 3 μm. When the average particle size is 0.5 μm or less, the effect of improving the slipperiness is insufficient, and when the average particle size is 5 μm or more, the transparency is easily impaired.
The average particle diameter is measured with a Multisizer II precision particle size distribution measuring apparatus manufactured by BECKMAN COULTER.
The inert particles are usually contained in the skin layer in an amount of 0.005 to 0.1% by weight, preferably 0.01 to 0.07% by weight. The above range is preferable in terms of improving slipperiness without impairing transparency.

Examples of the inert particles of the present invention include inorganic particles, such as metal oxides (eg, aluminum oxide, titanium dioxide, silicon dioxide, magnesium oxide, zinc oxide, zirconium oxide), metal carbonates (eg, magnesium carbonate, carbonic acid). Calcium, barium carbonate), metal sulfates (eg calcium sulfate, barium sulfate), metal phosphates (eg calcium phosphate, lithium phosphate), viscosity minerals (eg kaolin, clay, bentonite), calcium phosphate It can be illustrated.
In particular, silicon dioxide is preferable because it has a refractive index close to that of saturated polyester and does not impair transparency.

(Multilayer preform molding)
A multilayer preform having a skin layer and a core layer can be obtained by multilayer molding using two kinds of resins, polyester containing inert particles and polyester not containing inert particles.
Multilayer preform molding is described, for example, in JP-A-3-292109. Although the heating temperature of the resin at the time of preform molding varies depending on the resin used, it is, for example, 270 to 320 ° C, preferably 270 to 310 ° C. In the multilayer preform, first, a polyester resin containing inert particles constituting the skin layer is injected by a main cylinder, and then the polyester resin containing no inert particles constituting the core layer is slightly shifted in timing. It can be made by injecting with a cylinder and finally also by injecting a polyester resin containing inert particles with a main cylinder.

Since the core layer does not affect the bottle slipperiness, it can be composed of polyester resin that does not contain inert particles, and can use general-purpose polyester resin with excellent transparency and economy. It is possible to produce a bottle that satisfies both of the properties.
Moreover, you may crystallize the preform obtained by heating the plug part of a preform before blow molding as needed.

When blending inert particles into the polyester resin of the skin layer, it is possible to dry blend just before molding, but it is desirable to use a masterbatch in which inert particles are melted and kneaded in advance from the viewpoint of equipment contamination. .

(Hollow molding)
The hollow molded body of the present invention can be obtained by biaxial stretching blow molding (hollow blow) molding of the above multilayer preform.
Multilayer hollow blow molding is described, for example, in JP-A-3-292109. The preform can be heated to a suitable stretching temperature, and then the preform is held in a mold having a desired shape, and then air is blown into the mold so as to manufacture the preform.
More specifically, the preform is blown by heating to an appropriate stretching temperature using a near infrared heater or the like. The heating temperature at the time of blow molding is usually 80 to 130 ° C, particularly preferably 90 to 120 ° C. The blow mold temperature is usually 20 to 170 ° C., preferably 20 to 160 ° C. In addition, a so-called two-stage blow molding method in which a bottle larger than the required bottle capacity is formed as necessary, the bottle is shrunk in a heating oven, and the shrunken bottle is blown again to form a bottle. Can adopt a multistage blow molding method of three or more stages.

The hollow molded body of the present invention preferably has a coefficient of static friction between bottles of less than 1.00 and a bottle Haze of 7.0 or less.
The static friction coefficient is more preferably less than 1.00, and particularly preferably 0.90 or less.

It is preferable for the static friction coefficient to be in the above-mentioned range because the friction is small and the bottles can be prevented from coming into close contact with each other during transportation or the like.
The static friction coefficient is measured according to JIS P8147 '94. Specifically, the bottles are placed in two stages on the table of the friction measuring device (AN manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the table is tilted at a constant speed (2.6 ° / sec). The angle (θ) at which sliding starts is measured and calculated from tan θ.

Haze is measured three times using a haze meter (NDH2000 manufactured by Nippon Denshoku Co., Ltd.) for the bottle body section obtained by blow molding, and the average value is evaluated.
When the haze is in the above range, it can be suitably used as a beverage container.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited only to the aspect of these Examples.

(Example 1)
Polyethylene terephthalate (a) having an intrinsic viscosity (IV) of 0.76 dl / g and a diethylene glycol content of 2.4 mol%, and natural EPM7E937 (silicon dioxide-containing masterbatch polyethylene terephthalate) manufactured by Sumika Color Co., Ltd. in the polyethylene terephthalate (a). The polyethylene terephthalate (b) mixed with 0.6% by weight was dried at 150 ° C. under reduced pressure for about 16 hours. The average particle size of silicon dioxide contained in the master batch was 1.4 μm.
Thereafter, using the M-100A two-kind / three-layer molding machine manufactured by Meiki Seisakusho, the above (a) and (b) were injected at a barrel set temperature of 270 to 290 ° C., a screw rotation speed of 130 rpm, and a molding cycle of around 60 sec. A multilayer preform having a body thickness of 4.1 mm and a weight of 65 g was formed. The preform has a body skin layer 0.8 mm of polyethylene terephthalate (b) and a core layer 3.3 mm of polyethylene terephthalate (a).

Next, a preform was prepared by crystallizing only the plug part with a home-made crystallization apparatus. This plug part crystallization preform was made into a biaxial stretch blow molding machine SIDEL-LBO-No. 2 under the conditions of a blowing pressure of 35 kg / cm 2, a stretching temperature of 105 ° C., and a mold body surface temperature of 130 ° C., 2.0 times in length and 4.0 times in width (major axis), 3.4 times (short) Diameter) was biaxially stretched to produce a 2L square biaxially stretched bottle. Subsequently, the bottle was stored at room temperature for 24 hours, and the bottle static friction coefficient was measured.

(Example 2)
Molded in the same manner as in Example 1 except that 1.0% by weight of natural EPM7E937 (silicon dioxide-containing masterbatch polyethylene terephthalate) manufactured by Sumika Color used in Example 1 was mixed.

(Comparative Examples 1-5)
Molded in the same manner as in Examples 1 and 2, except that only the polyethylene terephthalate (b) used in Examples 1 and 2 was used for the skin and core layer.

  The comparative example 1 which does not use the silicon dioxide which is an inert particle has inadequate slipperiness, and the comparative examples 2-5 which use silicon dioxide also for a core layer are inferior to transparency.

Claims (3)

A saturated polyester resin multilayer preform formed of at least two layers of a saturated polyester resin layer including a skin layer and a core layer. The inert polyester having an average particle size of 0.5 to 5 μm in the saturated polyester resin forming the skin layer A multilayer polyester preform made of saturated polyester resin, characterized by containing particles. A multi-layer bottle made of saturated polyester resin obtained by stretching the multi-layer preform made of saturated polyester resin according to claim 1. The multilayer polyester bottle made of a saturated polyester resin according to claim 2, wherein the coefficient of static friction between the bottles is less than 1.00, and the bottle Haze is 7.0 or less.