JP2011161705A - Method of manufacturing thermoplastic resin molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a thermoplastic resin molding having excellent resistance to thermal shrinkage, e.g. a polyester resin molding, which enables simple and inexpensive manufacture without complicated equipment or troublesome operation. <P>SOLUTION: The method of manufacturing the thermoplastic resin molding is characterized by impregnating a to-be-treated material consisting of a thermoplastic resin, e.g. a polyester resin, having carbonyl-containing repeated units in the principal chain with an aldehyde compound and drawing the resultant resin. The aldehyde compound is preferably a 1-10C one, e.g. acetaldehyde, propionaldehyde or benzaldehyde. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a thermoplastic resin molded article such as a polyester resin molded article having excellent heat shrinkage resistance, and a thermoplastic resin molded article obtained by the method.

  Thermoplastic resins having a repeating unit containing a carbonyl group in the main chain, such as polyester resins, especially polyethylene terephthalate, are excellent in mechanical properties, heat resistance, chemical resistance, gas barrier resistance, etc. It is used. In addition, containers made of blown saturated polyester resin (blow bottles), particularly so-called PET bottles (polyethylene terephthalate containers), are widely used as carbonated drinks, drinks such as tea and coffee, foods, and cosmetics. Has been.

  However, when such a polyester container is filled with the contents at a high temperature or sterilized at a high temperature, there is a problem that the container main body, particularly the bottom of the container, is likely to undergo thermal contraction or thermal deformation. As a method for suppressing such heat shrinkage and thermal deformation during high temperature filling, a heated pressure fluid is fed into a test tubular preform (bottom cylindrical parison) prepared by injection molding, compression molding or the like in advance. When producing the container, a multistage blow molding method is employed in which the container is molded at a temperature 20 ° C. or more higher than the glass transition temperature and repeatedly expanded and contracted. In addition, a method of suppressing heat shrinkage by heat setting (heat setting) at a relatively high temperature after blow molding is also performed. A PET bottle imparted with heat resistance in this way is referred to as a heat-resistant PET bottle. However, in the above method, the operation is complicated. Moreover, it cannot be said that the effect of suppressing thermal contraction at the bottom of the container is sufficient. Non-Patent Document 1 reports that when a polyethylene terephthalate sheet is stretched at a high speed of 100 ° C. or higher at a high speed of 2 times or more, crystallization that hardly causes thermal shrinkage occurs. However, this method requires large-scale equipment and is not suitable for small-lot production.

  As another method for improving the heat resistance of a polyester container, there is a method of obtaining a heat-resistant container by blow-molding a heat-resistant resin with a polyester resin by co-extrusion molding, multistage injection molding or the like. However, this method has a drawback that the laminating process is complicated and the manufacturing apparatus is expensive. Furthermore, as a method for reducing thermal shrinkage and thermal deformation of the polyester resin molded body, a method of blending polyethylene terephthalate with polybutylene terephthalate, polyarylate, or the like has been proposed (Patent Documents 1 to 3). However, in these methods, it is necessary to produce a plurality of types of polymers, and there is a disadvantage that the number of steps increases and the cost increases. In addition, there is a similar problem in a molded body made of a thermoplastic resin having a repeating unit containing a carbonyl group in the main chain other than the polyester resin.

JP-A-5-178338 JP-A-8-3430 JP-A-10-176102

Polymer Engineering and Science, February 1996, Vol. 36, No. 4

  Therefore, an object of the present invention is to provide a method capable of easily and inexpensively producing a thermoplastic resin molded article such as a polyester resin molded article having excellent heat shrinkage resistance without requiring a complicated apparatus or complicated operation, and a heat resistance An object of the present invention is to provide a thermoplastic resin molded article having excellent shrinkage.

  Polyester resins such as polyethylene terephthalate are extremely stiff due to the stretching treatment near the glass transition temperature, but due to the influence of the amorphous state part excluding the part crystallized by stretching, , Heat shrinkage occurs. Therefore, heat shrinkage resistance is imparted by the heat treatment after the stretching treatment. Furthermore, these properties are generally discussed in terms of the degree of crystallinity of a polyester resin (eg, polyethylene terephthalate). The inventors have studied the difference in bond form between crystallization by heat treatment and crystallization by stretching treatment, based on the belief that the mechanical properties of polyester resin are also related to the bond properties between polyester molecules at the molecular chain ends. We are promoting.

  As a result of intensive studies to achieve the above object, the present inventors have impregnated a specific compound into an object to be processed consisting of a thermoplastic resin having a repeating unit containing a carbonyl group in the main chain, such as a polyester resin. By performing the stretching treatment, it has been found that shrinkage and deformation due to heat can be effectively suppressed, and for example, it has been found that a blow bottle having a very small shrinkage at the bottom can be easily produced even when high temperature filling is performed.

  That is, the present invention provides a molded thermoplastic resin product characterized by impregnating an object to be treated consisting of a thermoplastic resin having a repeating unit containing a carbonyl group in the main chain with an aldehyde compound and then subjecting it to a stretching treatment. Provide a method.

  As said aldehyde compound, a C1-C10 aldehyde compound is preferable.

  The present invention also provides a thermoplastic resin molded article obtained by the method for producing a thermoplastic resin molded article.

  According to the present invention, a thermoplastic resin molded article such as a polyester resin molded article excellent in heat-shrinkage resistance can be easily and inexpensively manufactured without requiring a complicated apparatus or a complicated operation. Such a thermoplastic resin molded article such as a polyester resin molded article is useful as, for example, a container for tea and coffee beverages (particularly a heat-resistant PET bottle) that can be filled at a high temperature.

  An important feature of the present invention resides in that an object to be treated consisting of a thermoplastic resin having a repeating unit containing a carbonyl group in the main chain is impregnated with an aldehyde compound and then subjected to a stretching treatment. The “stretching treatment” in the present invention includes blow molding accompanying stretching of a preform, stretching treatment of an unstretched film or sheet, and the like.

  The object to be treated consisting of a thermoplastic resin as an object to be impregnated with an aldehyde compound is a polymer itself obtained by polymerization (a lump, a powder, etc.), or a pellet obtained by extruding the polymer. In addition, a molded product before stretching treatment, which has been previously molded into a tube shape (test tube), a film (or sheet) shape, etc. by a well-known or conventional molding method (for example, injection molding, compression molding, extrusion molding, etc.) [Preform (parison) to be subjected to blow molding, film or sheet before stretching, etc.] may be used. The object to be processed made of a thermoplastic resin is preferably a molded product that has been previously formed into a tube shape, a film (or sheet) shape, or the like before stretching.

  The thermoplastic resin is not particularly limited as long as it is a thermoplastic resin having a repeating unit containing a carbonyl group in the main chain. Examples of such thermoplastic resins include polyester resins, polyamide resins (polyamide 6, polyamide 12, polyamide 11, polyamide 6-6, polyamide 6-12, etc.), polycarbonate resins, polyurethane resins, and mixtures thereof. It is done. Of these, polyester resins are particularly preferable. The number average molecular weight of the thermoplastic resin may be such that it can be molded, and is, for example, about 10,000 to 300,000.

  The polyester resin is not particularly limited as long as it is a thermoplastic resin having an ester bond in the main chain. The polyester resin can be produced by polycondensation of polycarboxylic acid and polyhydric alcohol, ring-opening polymerization of lactone, polycondensation of hydroxycarboxylic acid, or the like.

  Typical polyester resins include aromatic polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; aliphatic polyester resins such as polylactic acid and polycaprolactone; and mixtures thereof. Among these, polyethylene terephthalate is particularly preferable. The to-be-processed object which consists of polyester resins may contain thermoplastic resins other than a polyester resin. In that case, the ratio of the polyester resin to the total thermoplastic resin in the object to be treated is preferably 50% by weight or more, and particularly preferably 80% by weight or more (particularly 95% by weight or more).

  In the present invention, polyethylene terephthalate means a polyester having ethylene terephthalate units as main repeating units. “Main” means occupying 85% by weight or more of all repeating units. The same applies to polyethylene naphthalate and the like.

  Examples of polyvalent carboxylic acids other than terephthalic acid constituting polyethylene terephthalate include, for example, isophthalic acid, 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2-methylterephthalic acid, 4,4-stilbene dicarboxylic acid, naphthalene Aromatic dicarboxylic acids such as dicarboxylic acid, 4,4-biphenyldicarboxylic acid, orthophthalic acid, diphenoxyethanedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid; 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid And aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, and dodencandioic acid.

  Examples of polyhydric alcohols other than ethylene glycol that constitute polyethylene terephthalate include 1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, and 1,4-butanediol. Aliphatic diols such as 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol and diethylene glycol; Alicyclic rings such as 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol and hydrogenated bisphenol A And formula diols.

  Polyethylene terephthalate may contain oxyacid units such as p-β-hydroxyethoxybenzoic acid, p-oxybenzoic acid, and oxycaproic acid. The content of the oxyacid unit is preferably 30% by weight or less, particularly preferably 10% by weight or less, based on all repeating units constituting the polymer.

  When polyethylene terephthalate is used as the polyester resin, a polyester resin other than polyethylene terephthalate may be used in combination. In that case, the proportion of polyethylene terephthalate in the total polyester resin is preferably 50% by weight or more, and particularly preferably 80% by weight or more (particularly 95% by weight or more).

  Fillers, lubricants, colorants, light stabilizers, heat stabilizers, ultraviolet light absorbers, fluorescent brighteners, and other additives are added to the object to be processed made of thermoplastic resin such as polyester resin. Also good.

  In the present invention, examples of the aldehyde compound include aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, pentanal, hexanal, octanal, decanal, dodecanal, tetradecanal, hexadecanal, and octadecanal. Alicyclic aldehydes such as cyclohexanecarbaldehyde; aromatic aldehydes such as benzaldehyde, tolualdehyde, cinnamaldehyde, and naphthylaldehyde. Aldehyde compounds can be used alone or in combination of two or more.

  Among these, aldehydes having 1 to 10 carbon atoms (particularly aldehydes having 2 to 6 carbon atoms) are preferable. Moreover, in order to suppress coloring, an aliphatic aldehyde and an alicyclic aldehyde are preferable.

  In addition, as the aldehyde compound, a multimer of the aldehyde, or an aldehyde protected body in which the formyl group (—CHO) of the aldehyde is protected with a protecting group may be used. Examples of the aldehyde multimer include paraformaldehyde, trioxane, paraaldehyde, and metaaldehyde. Examples of the aldehyde protector include acetal derivatives such as dimethyl acetal of aldehyde, diethyl acetal of aldehyde, acetal of aldehyde with ethylene glycol, acetal of aldehyde with 1,3-propanediol, and the like.

  A method for impregnating an object to be processed made of a thermoplastic resin such as polyester resin with an aldehyde compound is not particularly limited, and can be appropriately selected according to the shape, size, and the like of the object to be processed. Examples of the impregnation method of the aldehyde compound include a method of immersing the object to be treated in a liquid aldehyde compound or a solution containing the aldehyde compound, and a method of mixing the object to be treated with a liquid aldehyde compound or a solution containing the aldehyde compound. Etc.

  In the case of using a solution containing an aldehyde compound, the solvent is not particularly limited as long as it does not impair the physical properties of the object to be processed and dissolves the aldehyde compound. Examples of the solvent include aliphatic hydrocarbons such as pentane, hexane, heptane and octane; aromatic hydrocarbons such as benzene, toluene and xylene; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; esters such as ethyl acetate Selected from among alcohols such as methanol, ethanol and isopropyl alcohol; water; and mixed solvents thereof. When using the solution containing an aldehyde compound, the density | concentration of an aldehyde compound is 5 weight% or more, for example, Preferably it is 10 weight% or more, More preferably, it is 50 weight% or more. By adjusting the concentration of the aldehyde compound, the penetration rate and the degree of penetration of the aldehyde compound into the object to be treated can be controlled.

  The temperature at which the aldehyde compound is impregnated into the object to be processed made of a thermoplastic resin such as polyester resin varies depending on the type and size of the object to be processed, the type of the aldehyde compound, etc., for example, −10 ° C. to 120 ° C. The temperature is preferably -10 ° C to 100 ° C, more preferably 0 ° C to 50 ° C, and particularly preferably about 10 to 40 ° C. Also, the impregnation time varies depending on the type and size of the object to be treated, the kind of aldehyde compound, and the like, and can be appropriately selected in consideration of the penetration rate of the aldehyde compound into the object to be treated and the production efficiency. The impregnation time is, for example, 0.1 second or longer (preferably 1 second or longer). The upper limit of the impregnation time is not particularly limited, but is preferably within 1 hour from the viewpoint of productivity and the like, and may be within 5 minutes (or within 1 minute). The amount of the aldehyde compound impregnated in the article to be treated made of a thermoplastic resin such as polyester resin varies depending on the kind of the article to be treated, but for example 0.01% by weight or more of the article to be treated after impregnation with the aldehyde compound, preferably 0 0.05% by weight or more, more preferably 0.1% by weight or more. Although there is no restriction | limiting in particular about the upper limit of the impregnation amount of this aldehyde compound, For example, it is less than 5 weight% (or less than 3 weight%).

  After impregnating the aldehyde compound into the object to be processed made of a thermoplastic resin such as polyester resin, depending on the shape and form of the object to be processed, drying, wiping, etc. Aldehyde compounds may be removed.

  Molded product before stretch treatment in which the object to be treated is previously formed into a tube shape (test tube), a film (sheet) shape, etc. [Preform (parison) to be subjected to blow molding, film or sheet before stretch, etc.] In this case, after impregnation with the aldehyde compound, it is subjected to a stretching treatment. In the case where the object to be treated is a polymer itself obtained by polymerization (such as a lump or powder), or a pellet obtained by extrusion molding of the polymer, first, after the impregnation with the aldehyde compound, the well known or It is formed into a tube shape (test tube), a film (sheet) shape or the like by a conventional molding method such as injection molding, compression molding, extrusion molding, etc., and then subjected to a stretching treatment.

  The stretching treatment is performed by a known or conventional method. For example, when an aldehyde compound is impregnated in a molded product (parison) molded in a tube shape (test tube), blow molding is performed while performing stretching by blow molding (preferably biaxial stretch blow molding). Goods (containers etc.) can be obtained. Although the temperature at the time of blow molding varies depending on the type of thermoplastic resin, for example, in the case of a polyethylene terephthalate resin or the like, it can be selected from a range of, for example, about 80 to 130 ° C., preferably about 100 to 120 ° C. As the stretch ratio of the blow molded product (blow bottle), for example, the stretch ratio in the axial direction of the body portion is preferably 1.5 times or more (particularly 2 times or more), and the stretch ratio in the circumferential direction is 2 times. It is preferable that it is above (especially 2.5 times or more).

  In addition, when the molded product formed into a film or sheet is impregnated with an aldehyde compound, for example, in the case of a polyethylene terephthalate resin or the like, it is preheated to 80 to 100 ° C., depending on the type of thermoplastic resin. A film (sheet) -like thermoplastic resin product can be obtained by stretching about 2.5 to 4.0 times in the vertical direction and then about 3 to 4.5 times in the horizontal direction at 95 to 120 ° C. .

  According to the present invention, since the object to be treated made of a specific thermoplastic resin is stretched in a state where the aldehyde compound is impregnated, the heat shrinkage resistance is greatly improved. Accordingly, heat setting (heat setting) after the stretching treatment is not necessarily required, but heat setting may be performed in order to further improve the heat shrinkage resistance. Although heat setting changes also with kinds of thermoplastic resin, it can be performed by heating at the temperature of about 100-235 degreeC, for example, Preferably about 100-160 degreeC. In addition, according to this invention, even when it is a case where heat setting is performed, compared with the past, the process of heat setting can be simplified (time reduction, temperature reduction, etc.). Therefore, a conventional molding machine can be used as it is without requiring a large-scale facility.

  The thermoplastic resin molded body (polyester resin molded body, etc.) obtained in this way has high rigidity and excellent heat shrinkage resistance and heat distortion resistance. , Heat shrinkage and thermal deformation of the bottom of the container are difficult to occur. Conventionally, various methods for removing acetaldehyde and formaldehyde from polyester resin molded bodies have been proposed. Rather, the polyester resin molding has so far been heat-shrinkable by applying a stretching treatment in a state of being actively impregnated with an aldehyde compound. It is surprising that the thermal properties, which have been regarded as important issues such as the body, have been greatly improved. The reason for this is not necessarily clear, but is presumed to be due to electrostatic interaction between partial charges of the aldehyde compound and the polymer molecule.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by these Examples.

Example 1 (acetaldehyde)
A test piece (dumbbell piece; see JIS K6251-8) (cross section thickness 0.5 mm, width 5.0 mm) was prepared from a polyethylene terephthalate film (a heat-resistant polyethylene terephthalate film manufactured by Teijin Chemicals Ltd.). After this test piece was immersed in acetaldehyde for 5 minutes at room temperature (25 ° C.), the test piece was taken out and stretched 2.1 times in the length direction at 100 ° C. using a tensile tester (stretching). (Magnification 2.1 times; tensile speed 30 mm / min). After cooling the test piece to room temperature, it was immersed in warm water of 95 ° C. for 10 minutes and taken out. It was 26% when the heat shrinkage rate was calculated | required by the following formula. The film after the test was slightly cloudy, but it was stretched cleanly without cracks. In addition, the length of the film in the following formula means the distance between chucks.
Thermal shrinkage rate (%) = {1- (film length after immersion in hot water−initial film length) / (film length immediately after stretching−initial film length)} × 100

Example 2 (acetaldehyde)
The same operation as in Example 1 was performed except that it was immersed in acetaldehyde for 1 minute. As a result, the heat shrinkage rate was 18%. The film after the test was slightly cloudy, but it was stretched cleanly without cracks.

Example 3 (benzaldehyde)
The same operation as in Example 1 was performed except that benzaldehyde was used instead of acetaldehyde. As a result, the heat shrinkage rate was 26%. The film after the test was yellowish.

Example 4 (benzaldehyde)
The same operation as in Example 1 was performed except that benzaldehyde was used instead of acetaldehyde and the immersion time was 1 minute. As a result, the heat shrinkage rate was 19%. The film after the test was more cloudy than in the case of acetaldehyde.

Comparative Example 1 (untreated)
The same operation as in Example 1 was performed except that the operation of immersing in acetaldehyde for 5 minutes was not performed. As a result, the heat shrinkage rate was 88%.

Comparative Example 2 (acetic anhydride)
The same operation as in Example 1 was performed except that acetic anhydride was used instead of acetaldehyde. The test was stopped because the film cracked during immersion in acetic anhydride.

Comparative Example 3 (acetic anhydride)
The same operation as in Example 1 was performed except that acetic anhydride was used instead of acetaldehyde and the immersion time was 1 minute. As a result, the heat shrinkage rate was 82%.

Comparative Example 4 (acetone)
The same operation as in Example 1 was performed except that acetone was used instead of acetaldehyde. The test was stopped because cracks occurred during film stretching.

Comparative Example 5 (ethyl acetate)
The same operation as in Example 1 was performed except that ethyl acetate was used instead of acetaldehyde. The test was stopped because cracks occurred during film stretching. The film was slightly cloudy.

Comparative Example 6 (ethyl acetate)
The same operation as in Example 1 was performed except that ethyl acetate was used instead of acetaldehyde and the immersion time was 1 minute. As a result, the heat shrinkage rate was 100%.

Comparative Example 7 (ethanol)
The same operation as in Example 1 was performed except that ethanol was used instead of acetaldehyde. As a result, the heat shrinkage rate was 91%. The cloudiness of the film was not seen.

Comparative Example 8 (toluene)
The same operation as in Example 1 was performed except that toluene was used instead of acetaldehyde. As a result, the heat shrinkage rate was 88%.

Comparative Example 9 (immersion in acetaldehyde after film stretching)
The same operation as in Example 1 was performed except that the film was first stretched 2.1 times in the length direction at 100 ° C. and then immersed in acetaldehyde for 5 minutes. As a result, the heat shrinkage rate was 88%. The reason why the heat shrinkage rate is not improved is considered to be that when the polyethylene terephthalate film is stretched 2.1 times, the molecular chains of the polyester are closer to each other and the aldehyde compound cannot penetrate.

  The above results are summarized in Table 1. In Examples 1 and 2, and Examples 3 and 4, there is a slight difference in thermal shrinkage, but this is within the error range, and an effect of the average value can be expected regardless of the impregnation time.

Claims (3)

  A method for producing a thermoplastic resin molded article, comprising: impregnating an object to be treated comprising a thermoplastic resin having a repeating unit containing a carbonyl group in the main chain with an aldehyde compound, and then subjecting the article to stretching treatment.   The method for producing a thermoplastic resin molded article according to claim 1, wherein the aldehyde compound is an aldehyde compound having 1 to 10 carbon atoms.   The thermoplastic resin molding obtained by the manufacturing method of the thermoplastic resin molding of Claim 1 or 2.