JP3860189B2 - Method for producing amorphous polyester resin - Google Patents

Description

  The present invention relates to a method for producing an amorphous polyester resin from a crystalline or semi-crystalline polyester resin.

  Polyester resins represented by polyethylene terephthalate (PET) are widely used as polymers for fibers, sheets and films. As for PET, crystalline polyethylene terephthalate (hereinafter referred to as “C-PET”) and amorphous polyethylene terephthalate (hereinafter referred to as “A-PET”) are obtained by a processing method. C-PET and A-PET are both synthesized by polycondensation of ethylene glycol and terephthalic acid. When rapidly cooled from the melted state, solid-state A-PET is obtained, and when gradually cooled, C-PET is obtained. C-PET is a state in which the molecules of the crystallized portion are regularly arranged, the density is high, and the intermolecular distance is short. In this state, strength, heat resistance, etc. are higher than the amorphous state, but impact resistance, transparency There was a problem that the processability was low.

  On the other hand, A-PET is characterized by high transparency, high impact strength, excellent workability, and does not generate toxic gas even when burned. Has been commercialized as an application, but since the A-PET changes from the amorphous state to the crystalline state by heating in the cylinder during the molding process by extrusion, it is difficult to stably knead and transfer the material. Met. In addition, since A-PET has a crystalline resin matrix as it is, the amorphous part is crystallized due to long-term use or thermal history, and internal stress is generated due to density change, so that the polymer chain is cut and flexible. , Impact resistance, strength and the like are extremely low.

  In order to overcome such drawbacks, conventionally, in order to reduce the crystallinity of the polyester resin as much as possible, a method of causing steric hindrance by blending a modified resin of PET and PET and making it difficult to crystallize, PET and polyester polycarbonate A method of producing a non-crystalline polyester resin by transesterification by melt mixing in the presence of an aliphatic metal salt, and a method of improving low temperature toughness and heat stability by adding a polyester elastomer to the crystalline polyester In addition, a method for providing a polyester excellent in heat resistance without loss of flexibility due to thermal history by using a polyester copolymer having a branched or crosslinked structure, and an amorphous copolyester using various diols and dicarboxylic acids Etc. have been proposed (Patent Document 1). Synthesis merging techniques, non-crystalline polymers of a wide, it is required such complicated kneading, the residual harmful metal salts, there are drawbacks such as poor secondary processability of the crosslinked resin.

By the way, it is known to modify a polyester by adding a bisoxazoline compound to a polyester resin. For example, it increases the degree of polymerization, suppresses decomposition at high temperatures, and maintains toughness such as flexibility and impact resistance for a long time. It has been reported that recovered polyester can be regenerated (Patent Document 2). However, there is no report about making a crystalline or semi-crystalline polyester resin into an amorphous polyester resin by adding a bisoxazoline compound.
JP-A-11-310690, JP-A-4-318059, JP-A-2-294357, JP-A-2-208352, JP-T-2003-501532 JP-A-56-18617, JP-A-2-208352, JP-A 2000-290362

  An object of the present invention is to provide a method for producing an amorphous polyester resin that eliminates the above-described defects, has little deterioration in flexibility and strength even after long-term use or thermal history, and is excellent in transparency. Let it be an issue.

As a result of intensive studies to solve such problems, the present inventors have added a small amount of 2,2′-tetramethylenebis (2-oxazoline) excellent in reactivity and compatibility to the polyester resin. The inventors have found that the object can be achieved and have reached the present invention.
That is, the present invention
(1) Amorphous, characterized by adding 0.001 to 0.05 parts by weight of 2,2′-tetramethylenebis (2-oxazoline) to 100 parts by weight of a crystalline or semicrystalline polyester resin A method for producing a reactive polyester resin,
(2) The method for producing an amorphous polyester resin according to (1), wherein the polyester resin is a polyethylene terephthalate resin,
Is to provide.

  According to the present invention, 2,2′-tetramethylenebis (2-oxazoline) reacts with the residual carboxyl group of the polyester resin to break the structural symmetry of the polyester resin. Therefore, it is possible to produce an amorphous polyester resin that is less likely to have a decrease in flexibility and strength even when used for a long time or has a thermal history, and that is excellent in transparency, at low cost.

Hereinafter, the present invention will be described in detail.
In the present invention, 2,2′-tetramethylenebis (2-oxazoline) is added to a crystalline or semicrystalline polyester resin and reacted.
In the present invention, the crystalline polyester resin means a crystallinity of 35% by weight or more, and the non-crystalline polyester resin means a crystallinity of 5% by weight or less.

  The polyester resin used in the present invention is a crystalline or semi-crystalline polyethylene terephthalate thermoplastic resin. The polyethylene terephthalate resin is a resin composed of a dicarboxylic acid unit mainly composed of terephthalic acid units and a diol unit mainly composed of ethylene glycol units. Examples of the polyethylene terephthalate resin include a polyethylene terephthalate resin composed only of a terephthalic acid unit and an ethylene glycol unit, and a part of the terephthalic acid unit is replaced with another dicarboxylic acid unit and / or a part of the ethylene glycol unit is replaced with another part. Any polyethylene terephthalate resin substituted with a diol unit can be used.

  Examples of other dicarboxylic acid units that the polyethylene terephthalate resin may have include isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid , Aromatic dicarboxylic acids such as diphenyl ether dicarboxylic acid and diphenylsulfone dicarboxylic acid, alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, malonic acid , Dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, sebacic acid, suberin Aliphatic dicarbo such as acid Acid, and dicarboxylic acid units derived from such ester-forming derivatives thereof are go up. The polyethylene terephthalate-based resin may have only one kind or two or more kinds of the other dicarboxylic acid units described above.

  Examples of other diol units that the polyethylene terephthalate resin may have include tetramethylene glycol, hexanemethylene glycol, decamethylene glycol, neopentyl glycol, diethylene glycol, propylene glycol, 2-methylpropanediol, 1,5- Aliphatic diols such as pentanediol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol, cyclohexanediol, 2,2-bis (4-β-hydroxyethoxyphenyl) propane, 2,2-bis (4 -Low molecular weight polyalkyls such as aromatic diols such as -β-hydroxyethoxyphenyl) sulfone, diethylene glycol, polyethylene glycol, poly-1,3-propylene glycol and polytetramethylene glycol Examples include diol units derived from lenglycol and the like. The polyethylene terephthalate-based resin may have only one kind of other diol units described above, or may have two or more kinds.

  As the polyethylene terephthalate resin, a virgin product may be used alone, a recycled product may be used alone, or a virgin product and a recycled product may be mixed and used. Here, the recycled product is a polyethylene terephthalate resin and a used PET bottle, a used polyethylene terephthalate resin fiber, a used polyethylene terephthalate system having a history of passing through a molding machine or a spinning device in a heated and melted state. It is obtained by collecting resin molded products.

The bisoxazoline compound added to the polyester resin is 2,2′-tetramethylenebis (2-oxazoline), which is highly reactive, has no by-products during the reaction, has excellent compatibility, and is flexible. It is done.
The addition amount of 2,2′-tetramethylenebis (2-oxazoline) needs to be 0.001 to 0.05 parts by weight with respect to the polyester resin. If the amount is less than this, a sufficient crystallization inhibitory effect is not exhibited. On the other hand, even if it is used in excess of this, the degree of crystallinity exceeds 5%, and an amorphous polyester resin cannot be obtained. That is, when the addition amount of 2,2′-tetramethylenebis (2-oxazoline) is about 1 to 0.1% by weight of a normal bisoxazoline compound, an amorphous polyester cannot be obtained. As the amount is reduced, the crystallinity is surprisingly reduced and an amorphous polyester is produced.

Although 2,2′-tetramethylenebis (2-oxazoline) needs to be reacted with the polyester resin, the method is arbitrary and can be added and reacted when the polyester resin is produced. Or it is more preferable to add and react at the time of a shaping | molding process.
As a reaction at the time of pellet production or molding, conventionally known equipment and methods can be used as a resin composition preparation method, and it can be easily put in a molten state above the melting point of the polyester resin and below the decomposition point. To be implemented. For example,
(1) A method of mixing each component, kneading and extruding with an extruder to prepare pellets, and then molding (2) A method of once preparing pellets having different compositions, and mixing and molding the pellets in a predetermined amount (3) Any method including directly charging each component into a molding machine can be used.
Further, in order to uniformly mix the additive components, a method in which a part of the resin component is mixed as a fine powder with other components, or 2,2′-tetramethylenebis (2-oxazoline) is added. A method of mixing and using a masterbatch obtained by pelletizing a polyester resin containing at a concentration and a polyester resin is preferable.

  The polyester resin used in the present invention is a stabilizer such as an antioxidant or an ultraviolet absorber, an antistatic agent, a flame retardant, a colorant such as a dye or pigment, and the like, as long as the effect of the present invention is not impaired. You may contain the additive of well-known thermoplastic resins, such as a lubricant for improving fluidity | liquidity and mold release property, a lubrication agent, and an inorganic substance. In particular, when used at a high temperature of 50 ° C. or higher for a long period of time, it is preferable to add a stabilizer to prevent discoloration. The addition of antioxidant is preferred. As a stabilizer at that time, a hindered phenolic antioxidant and / or a sulfurous antioxidant are preferably used from the viewpoint of a large stabilizing effect, and in particular, the combined use of both is more preferably used from the viewpoint of a larger stabilizing effect. It is done.

  Specific examples of hindered phenol antioxidants that can be preferably used include 2,6-di-tert-butyl-4-methylphenol, n-octadesyl-3- (3 ′, 5′-tert-butyl-4) -Hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2-t-butyl-6- (3'-t-butyl-5-methyl-2'hydroxybenzyl)- Examples include 4-methylphenyl acrylate.

  Specific examples of sulfur-based antioxidants that can be preferably used include dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropioate. Nate is listed.

  The addition amount of the hindered phenol-based antioxidant and / or the sulfur-based antioxidant (the total addition amount when two or more antioxidants are contained) is 0.01 to the total amount of the polyester resin composition. 5% by weight, preferably 0.02 to 3% by weight.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. In the following, parts and% indicate parts by weight and% by weight, respectively. In addition, the measurement or evaluation of various physical properties in the examples was performed as follows.

(1) Appearance transparency: The appearance transparency of the pellets and the press film was visually evaluated in the following three stages.
○: Transparent, △: Translucent, ×: Whitening (opaque)
(2) Crystallinity: The crystallinity of the polyester resin was calculated by measuring the density of the pellets of the composition.
The pellet density was measured according to JIS K 7112 (measurement temperature = 23 ° C.), and the degree of crystallinity was calculated from Equation 1.

(3) Tensile strength and tensile elongation: Using a 200 μm thick press film, five 100 mm × 15 mm test pieces were sampled and subjected to a tensile test at a speed of 100 mm / min. The average value was calculated.

Examples 1-3 and Comparative Examples 1-5
A pre-dried polyethylene terephthalate resin (manufactured by Unitika Ltd., bottle pellets NEH-2050, intrinsic viscosity = 0.78) and a bisoxazoline compound were premixed in the ratio shown in Table 1, and then a twin screw extruder (stock) PCM-30 manufactured by Ikekai Tekko Co., Ltd.), melted and kneaded at 270 ° C., extruded into a strand, cooled with water, cut and pelletized. After sufficiently drying the resulting polyester resin composition pellets, the appearance transparency of the pellets was evaluated by visual observation, and the crystallinity of the pellets was calculated by density measurement. The results are shown in Table 2.
Next, using these pellets, a press film having a thickness of 200 μm was manufactured by a hot press at 270 ° C. After the press film was allowed to stand for 24 hours under the condition of 23 ° C. × 50% RH, a test piece of 100 mm × 15 mm was collected, and the appearance transparency was evaluated and the tensile breaking strength and the elongation were measured. The results are shown in Table 2 as initial values.
The various press films were allowed to stand for 60 days under the condition of 50 ° C. × 50% RH, and then test pieces were similarly collected, and the appearance transparency was evaluated and the tensile breaking strength and the elongation were measured. The results are shown in Table 2 as values after heat history.

  As described above, according to the present invention, by adding a small amount of 2,2′-tetramethylenebis (2-oxazoline), there is little decrease in flexibility and strength due to long-term use or heat history, Moreover, since an amorphous polyester resin excellent in transparency can be produced at low cost, it can be suitably used for applications such as films, plates, clear cases, trays and the like.

Claims (2)

  Amorphous polyester resin characterized by adding 0.001 to 0.05 parts by weight of 2,2'-tetramethylenebis (2-oxazoline) to 100 parts by weight of crystalline or semi-crystalline polyester resin and reacting them. Manufacturing method.   The method for producing an amorphous polyester resin according to claim 1, wherein the polyester resin is a polyethylene terephthalate resin.