JP2006111007A - Manufacturing method of paper laminated by laminated polyester and container made of paper laminated with polyester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a paper laminated by a polyester superior in an extrudability, a processability of a container and superior in both of a color tone and an adhesion, the polyester laminated paper made by the method and a paper container made by using the above. <P>SOLUTION: The method for producing the polyester laminated paper comprises laminating at least two kinds of polyester resins with a butylene terephthalate repeating unit as a main component on at least one surface of a paper by a coextrusion, as a resin (A) used to overlie the top surface of paper, a resin with a melt viscosity of ≤500 Pa S at 250°C and a shear rate of 91.2 sec<SP>-1</SP>is used and as a resin (B) to be used on an opposite side of the paper on a layer containing the resin (A), a resin having a melt tension of ≥1.0 mN at 250°C is used, and each of the resin (A) and resin (B) is laminated so as a ratio of film thickness d(resin B)/d(resin A) after the lamination to be 0.5-50. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a laminated polyester laminated paper in which a plurality of polyester resins having specific physical properties having a butylene terephthalate unit as a main repeating unit are laminated and laminated on the paper surface. Specifically, a method for producing a laminated polyester laminated paper excellent in extrudability, container processability and color tone, and also excellent in adhesion between the paper and the polyester film, a laminated polyester laminated paper obtained by the method, and It relates to the paper container used.

  In recent years, foods that are cooked by a microwave oven, an oven, or the like have become widespread, and one of the containers is a container in which a synthetic resin is laminated on paper (hereinafter abbreviated as a laminated paper container). The laminated paper container has advantages in that it is lighter, cheaper and higher in heat resistance than a plastic container. In addition, it has the advantage of being able to inspect foreign matters in foods with a metal detector. It is used as cooking containers for confectionery, lunch boxes, side dishes cups, frozen food trays, etc. sold at stations, convenience stores, grocery stores, and the like.

  Synthetic resins used in laminated paper containers include polymethylpentene resins, polyolefin resins, polyester resins, etc. Among them, polyester resins are used for the transfer of plastic odors and paper odors to foods and foods. It has the best balance in terms of taste change, and also has good balance of performance, such as good heat resistance and processability, so it is used in various food fields.

  Patent Document 1 discloses a container for food packaging made of paper laminated with polyester containing polybutylene terephthalate (hereinafter sometimes referred to as PBT), and in particular specifies the ratio of the intrinsic viscosity of the resin before and after extrusion. It is disclosed that heat sealability is improved by maintaining the value above the value. However, the polyester specifically disclosed in the examples is only polyethylene terephthalate (hereinafter sometimes referred to as PET), and has a PBT having a melt viscosity of a specific value or less and a melt tension of a specific value or more. There is no suggestion that by laminating and laminating PBT, a laminated paper excellent in any of extrudability, container processability, color tone, and adhesion between paper and PBT can be obtained.

Patent Document 2 discloses a microwave heating paper container in which PBT is extruded and laminated, and a container using PBT resin is superior in heat resistance, food contamination, and food adhesion compared to a container using PET resin. It is disclosed that it is excellent in oxygen permeability and heat sealability. In Patent Document 2, in order to improve the adhesion between the PBT resin and the paper, it is necessary to use a pre-treated paper by corona discharge, and the adhesion is simply obtained by laminating the PBT resin on the paper. There was a problem that the manufacturing cost was not sufficient.
Also, by laminating and laminating PBT having a melt viscosity below a specific value and PBT having a melt tension above a specific value, any of extrudability, container workability, color tone, and adhesion between paper and PBT However, there is no suggestion that an excellent laminated paper can be obtained.

In Patent Document 3, a heat-resistant paper container for heat cooking formed by forming a laminate obtained by laminating a PBT resin having a terminal carboxyl group content of less than 60 meq / kg on heat-resistant paper has moldability and heat resistance. It is disclosed that it is suitable as a heat-resistant container for cooking at high temperature without being transferred to a food product. Also in this patent document 3, in order to improve the adhesion between the PBT resin and the paper, a paper pretreated by corona discharge is used, and the adhesion is simply obtained by laminating the PBT resin on the paper. There was a problem that it was not enough.
Also, by laminating and laminating PBT having a melt viscosity below a specific value and PBT having a melt tension above a specific value, any of extrudability, container workability, color tone, and adhesion between paper and PBT However, there is no suggestion that an excellent laminated paper can be obtained, and a laminated paper having excellent overall properties has been desired.

JP-A-55-166247 JP-A 64-70620 JP 2000-93296 A

  The present invention has been made in view of the above circumstances, and a solution to the problem is obtained by a method for producing a laminated polyester laminated paper excellent in all of extrudability, container processability, color tone, and adhesion, and the method thereof. Another object of the present invention is to provide a laminated polyester laminated paper and a paper container using the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that a polyester resin having a relatively low melt viscosity of a specific value or less and a polyester resin having a melt tension of a specific value or more on a paper in this order. And, by laminating and laminating so as to have a specific film thickness ratio, it has excellent overall characteristics, excelling in extrudability, container processability, color tone, and adhesion between paper and PBT. The present invention was completed by finding that a laminated laminate paper having the above can be obtained.

That is, the gist of the present invention is a method for producing a laminated polyester laminated paper in which at least two kinds of polyester resins having a butylene terephthalate repeating unit as a main component are laminated on at least one surface of paper by coextrusion. On the layer containing the resin (A), a resin having a melt viscosity of 500 (Pa · S) or less at 250 ° C. and a shear rate of 91.2 (sec ⁻¹ ) is used as the polyester resin (A) laminated on the side. Then, as the polyester resin (B) to be laminated on the side opposite to the paper, a resin having a melt tension of 1.0 mN or more at 250 ° C. is used, and the film thickness ratio after lamination (resin B) / d (resin A) The laminated polyester laminate is characterized by laminating the resins (A) and (B) so as to be 0.5 to 50 A method of manufacturing of over door paper, resides in. Moreover, it exists in the polyester laminated paper container formed by the polyester laminated paper obtained by the manufacturing method, and this processing.

  According to the present invention, a laminated polyester laminated paper which is remarkably improved in meandering, neck-in and the like of a film observed when producing a conventional laminated paper, and excellent in all of extrudability, container workability, color tone and adhesion. In particular, it is suitable as a base paper for heat-resistant food packaging containers that are cooked in a microwave oven or oven.

  Hereinafter, the present invention will be described in detail.

  The polyester resins (A) and (B) mainly composed of butylene terephthalate repeating units used in the present invention are polyesters laminated by coextrusion on paper, and 1,4-butanediol as a polyhydric alcohol component A polyester obtained by polymerization using terephthalic acid or an ester-forming derivative thereof as a polyvalent carboxylic acid component. The main repeating unit means that the butylene terephthalate unit is 70 mol% or more in the total polycarboxylic acid-polyhydric alcohol unit, preferably 80 mol% or more, more preferably 90 mol%, particularly 95 It is preferably at least mol%.

  Examples of polyvalent carboxylic acid components other than terephthalic acid that can be used in the production of the polyester resins (A) and (B) include 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and isophthalic acid. , Aromatic polycarboxylic acids such as phthalic acid, trimesic acid, trimellitic acid, aliphatics such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid Examples thereof include alicyclic dicarboxylic acids such as dicarboxylic acid and cyclohexanedicarboxylic acid, or ester-forming derivatives of the above polyvalent carboxylic acids (for example, lower alkyl esters of polyvalent carboxylic acids such as dimethyl terephthalate). These polyvalent carboxylic acid components may be used alone with terephthalic acid, or a plurality of them may be mixed with terephthalic acid.

  On the other hand, examples of polyhydric alcohol components other than 1,4-butanediol include aliphatic polyhydrides such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, pentanediol, hexanediol, glycerin, trimethylolpropane, and pentaerythritol. Monohydric alcohol, alicyclic polyhydric alcohol such as 1,4-cyclohexanedimethanol, aromatic polyhydric alcohol such as bisphenol A and bisphenol Z, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, etc. Examples include polyalkylene glycol. These polyhydric alcohol components may be used alone with 1,4-butanediol, or a plurality of these may be mixed with 1,4-butanediol.

  The polyester resins (A) and (B) of the present invention may be singular as long as the requirements of the present invention are satisfied, or a mixture of a plurality of polyesters having different terminal carboxyl group concentrations, melting points, catalyst amounts, etc. is melted. And may be molded.

  Further, when producing the polyester resins (A) and (B) used in the present invention, a titanium compound is usually used as a catalyst, and specific examples include inorganic titanium compounds such as titanium oxide and titanium tetrachloride, Examples thereof include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate. Among these, tetraalkyl titanates are preferable, and tetrabutyl titanate is particularly preferable among them.

  As the catalyst, in addition to the titanium compound, a tin compound may be used in combination as a catalyst. Specific examples of tin compounds include dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide, triisobutyl. Examples include tin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin sulfide, butylhydroxytin oxide, methylstannic acid, ethylstannic acid, and butylstannic acid.

  In addition to titanium compounds, magnesium compounds such as magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium alkoxide. Side, calcium compounds such as calcium hydrogen phosphate, antimony compounds such as antimony trioxide, germanium compounds such as germanium dioxide and germanium tetroxide, manganese compounds, zinc compounds, zirconium compounds, cobalt compounds, orthophosphoric acid, phosphorous acid, Phosphorous acid, polyphosphoric acid, phosphorus compounds such as esters and metal salts thereof, and reaction aids such as sodium hydroxide and sodium benzoate may be used in combination.

In the present invention, a polyester resin having a melt viscosity of 500 (Pa · S) or less at 250 ° C. and a shear rate of 91.2 (sec ⁻¹ ) is used as the polyester resin (A) laminated on the paper surface. It is characterized by. The melt viscosity can be measured by, for example, a Toyo Seiki Co., Ltd. Capillograph. Thereby, even when the melt tension of the polyester resin used for the polyester resin layer (B) laminated on the surface of the polyester resin layer (A) is relatively high, the adhesion between the paper and the polyester laminated film is improved. Is possible. If the melt viscosity exceeds 500 (Pa · S), the adhesion to paper tends to be lowered, and the container processability tends to be lowered. The upper limit of the melt viscosity is preferably 450 (Pa · S) or less, more preferably 400 (Pa · S) or less, still more preferably 380 (Pa · S) or less, particularly 350 (Pa · S) or less, On the other hand, the lower limit is preferably 100 (Pa · S) or more, more preferably 150 (Pa · S) or more, and still more preferably 200 (Pa · s). The polyester resin having this specific melt viscosity can be obtained by adjusting conditions such as polymerization time, degree of reduced pressure and temperature in the polyester production process.

  In the present invention, a polyester resin having a melt tension at 250 ° C. of 1.0 mN or more is used as the polyester resin (B) laminated on the side opposite to the paper on the layer containing the polyester resin (A). It is characterized by that. Thereby, a laminated paper having good high-speed laminating properties can be obtained. Here, melt tension can be calculated | required, for example using the Toyo Seiki Co., Ltd. product capillograph. The upper limit of the melt tension is preferably 10 mN or less, more preferably 7.0 mN or less, still more preferably 5.0 mN or less, most preferably 3.0 mN or less, while the lower limit is preferably 1.1 mN or more. 1.2 mN or more is more preferable. This polyester resin having a specific melt tension can be obtained by adjusting conditions such as polymerization time, degree of reduced pressure and temperature in the polyester production process.

  If the melt tension is less than 1.0 (mN), the neck-in phenomenon during extrusion is large, the difference in thickness between the polyester layer at the center and end after lamination is significantly large, and the laminated paper is molded into a container. When processing or when the container is bent, cracks and pinholes may occur in the polyester layer. On the other hand, if the melt tension greatly exceeds 10 (mN), the amount of extrusion is limited, and high-speed extrudability tends to decrease, and adhesion to paper tends to decrease.

  In the present invention, the polyester resins (A) and (B) can be produced either by a melt polymerization method or by a solid phase polymerization method after a melt polymerization reaction, and may be either a continuous method or a batch method. The melt polymerization method by the continuous method is preferable from the viewpoint of extrusion stability such that the extruder screw load during plasticization of the polymerized pellets is uniform and the film thickness unevenness on the paper is small. On the other hand, the pellets produced by the solid phase polymerization method described later tend to have uneven screw load, and when extruded near the upper limit of the screw load, there may be a case where the screw stops due to instantaneous overload, etc. Since the film thickness unevenness may increase, the melt polymerization method is preferred from the viewpoint of production efficiency.

  Although there is no restriction | limiting in particular in the method in the case of employ | adopting a melt-polymerization method in this invention, It is preferable to superpose | polymerize continuously using a serial continuous tank reactor. For example, a dicarboxylic acid component and a diol component are preferably heated at a temperature of 150 to 280 ° C., more preferably 180 to 265 ° C. in the presence of an esterification reaction catalyst in one or a plurality of esterification reaction vessels. Is 6.67 to 133 kPa, more preferably 9.33 to 101 kPa, and the esterification reaction is continued for 2 to 5 hours with stirring. Subsequently, the oligomer which is the obtained esterification reaction product is transferred to a polycondensation reaction tank, and preferably in the presence of a polycondensation reaction catalyst in one or a plurality of polycondensation reaction tanks, preferably 210 to 280 ° C. The polycondensation reaction can be carried out continuously for 2 to 5 hours with stirring under a reduced pressure of 220 to 265 ° C., preferably 26.7 kPa or less, more preferably 20 kPa or less. The polybutylene terephthalate resin obtained by the polycondensation reaction is usually transferred from the bottom of the polycondensation reaction tank to a polymer extraction die and extracted in the form of a strand. It is a pellet.

  The polyester resins (A) and (B) used in the present invention can also be produced by performing solid phase polymerization after melt polymerization. For example, in a melt polymerization method such as a batch method, a transesterification reaction or an esterification reaction and a polycondensation reaction are performed to obtain a polyester resin having a desired intrinsic viscosity, and then the resin is reduced under a reduced pressure of 1.33 to 26.6 kPa. It can be produced by solid phase polymerization under mild conditions such as heating at 160 to 170 ° C. for 1 to 2 hours.

  There is no restriction | limiting in particular in the type of the esterification reaction tank to be used, For example, a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower type continuous reaction tank, etc. can be mentioned. The esterification reaction tank may be one, or may be a plurality of tanks in which a plurality of tanks of the same kind or different kinds are connected in series. There is no restriction | limiting in particular in the type of the polycondensation reaction tank used for this invention, For example, a vertical stirring polymerization tank, a horizontal stirring polymerization tank, a thin film evaporation type polymerization tank etc. can be mentioned. The number of polycondensation reaction tanks can be one, or a plurality of tanks in which a plurality of tanks of the same or different types are connected in series can be used.

  The intrinsic viscosity of the polyester resin (A) of the present invention is preferably 0.5 dl / g or more, more preferably 0.6 dl / g or more, particularly preferably 0.7 dl / g or more, while the upper limit is 1.1 dl / g or less. Further, it is preferably 1.0 dl / g or less, particularly 0.9 dl / g or less. If the intrinsic viscosity of the polyester resin (A) is less than 0.5 dl / g, the mechanical strength of the molded product may be lowered. When the intrinsic viscosity exceeds 1.1 dl / g, the melt viscosity of the resin (A) becomes high, the fluidity is lowered, and the moldability may be lowered. Also, the polyester resin (A) and the paper surface Adhesion may be reduced.

  On the other hand, the intrinsic viscosity of the polyester resin (B) of the present invention is preferably 1.0 dl / g or more, more preferably 1.1 dl / g or more, and particularly preferably 1.2 dl / g or more, while the upper limit is 2.5 dl / g. Hereinafter, it is further preferably 2.0 dl / g or less, particularly 1.8 dl / g or less. If the intrinsic viscosity of the polyester resin (B) is less than 1.0 dl / g, the mechanical strength of the molded product may be lowered. When the intrinsic viscosity exceeds 2.5 dl / g, the melt viscosity of the resin (B) becomes high, the extruder screw load increases, the extrusion amount may be limited, and the pellet productivity may be significantly reduced. In the present invention, the intrinsic viscosity of PBT is a value determined from a solution viscosity measured at 30 ° C. using a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (weight ratio 1/1). .

  The temperature-falling crystallization temperature of the polyester resins (A) and (B) used in the present invention is preferably 170 ° C. or higher and more preferably 175 ° C. or higher from the viewpoint of heat resistance of the container after lamination. In the present invention, the temperature-falling crystallization temperature means a crystallization temperature measured with a differential scanning calorimeter at a temperature-falling rate of 20 ° C./min. The temperature-falling crystallization temperature is a temperature-falling rate of 20 from the melted state of PBT. It is the temperature of the exothermic peak due to crystallization that appears when cooled at ° C / min.

  The amount of terminal carboxyl groups of the polyester resins (A) and (B) used in the present invention is usually 50 eq / t or less. Preferably it is 30 eq / t or less, More preferably, it is 25 eq / t or less. The amount of terminal carboxyl groups can be determined by dissolving PBT in an organic solvent such as benzyl alcohol and performing neutralization titration using a benzyl alcohol solution such as sodium hydroxide. By making the amount of terminal carboxyl groups of PBT 50 eq / t or less, the heat aging stability (residence stability) of the resin composition of the present invention can be particularly improved, and the hydrolysis resistance is remarkably enhanced. Can do.

  The polyester resins (A) and (B) used in the present invention preferably each have a total content of titanium atoms and tin atoms of 100 ppm or less. These atoms are contained as a titanium compound or a tin compound that is a catalyst residue of the polymerization reaction. When a tin compound other than the titanium compound is not used as a catalyst, the polyester resins (A) and (B) contain substantially no tin atom, and therefore, a polyester resin having a titanium atom content of 100 ppm or less is preferable.

  Furthermore, in the present invention, it is preferable that the content of each titanium atom itself in the polyester resins (A) and (B) is a specific amount from the viewpoint that the color tone change of the laminated paper is small. Specifically, the lower limit of each titanium atom content in the polyester resins (A) and (B) is preferably 10 ppm or more, more preferably 15 ppm or more, and further preferably 20 ppm or more. On the other hand, the upper limit is preferably 90 ppm or less, more preferably 85 ppm or less, still more preferably 80 ppm or less, and particularly preferably 70 ppm or less. When the content of titanium atoms is more than 100 ppm, the necking-in phenomenon of the polyester during extrusion laminating tends to increase, yellowing of the polyester after extrusion laminating and fish eyes tend to become remarkable, and food is filled. When the container is heated at a high temperature for a long time, the appearance change or the taste of the food contact portion may change. On the other hand, when it is less than 10 ppm, the polyester polymerization efficiency tends to decrease. The content of titanium atom or tin atom should be measured using a method such as atomic emission, atomic absorption, Induced Coupled Plasma (ICP) after recovering the metal in the polymer by a method such as wet ashing. I can do it.

  In the polyester resins (A) and (B) of the present invention, a reinforcing filler can be blended as long as the characteristics of the present invention are not impaired. The reinforcing filler may be organic or inorganic. Specific examples include glass fiber, glass flake, milled fiber, glass bead, montmorillonite, mica, talc, kaolin, carbon fiber, whisker, wollastonite, silica, calcium carbonate, barium sulfate, titanium oxide, alumina and the like. . These may be used alone or in combination.

  Further, the polyester resins (A) and (B) of the present invention include resins other than polyester (for example, engineering plastics such as polyolefin resin, vinyl resin, polyamide, polyphenylene ether, etc.) within the range not impairing the characteristics of the present invention. Rubber, etc.), organic crosslinked particles, inorganic particles, etc., and a third component such as a heat stabilizer, an antioxidant, an antistatic agent, a release agent, a colorant, and a printability improving agent may be blended in an appropriate amount.

  In the present invention, the method of blending the above-mentioned various additives and other resins into the polyester resins (A) and (B) is not particularly limited as long as it is a known method. For example, (1) polyester resin A method of adding at the production stage, (2) a method of dry blending with a pellet-shaped polyester resin, and (3) a masterbatch in which a part of the polyester resin is premixed with other resins or additives, and the rest Or a method of adding the polyester resin during melt kneading when laminating the polyester resin.

  The paper used in the present invention includes paper and paperboard based on the classification of the Japan Paper Association and non-woven fabric. Paper based on the classification of the Japan Paper Association includes processed base paper such as cup base paper, pure white roll paper, wrapping paper such as kraft paper, printing and information paper such as high-quality paper and inkjet paper, and synthetic resin fibers such as polyester fiber And a functional paper blended with, and examples of the paperboard include coated cardboard. Among them, paperboard paperboard, pure white roll paper, and bleached kraft paper are preferable from the viewpoint of food container molding. The paper may be colored on the entire surface, or previously printed with characters, patterns, pictures, etc. on the surface.

In addition, the smoothness of the paper of the present invention determined by measurement in accordance with JIS P8119 is preferably 10 seconds or more, more preferably 50 seconds or more, and still more preferably 100 seconds in terms of adhesion to polyester. More preferably, it is 200 seconds or more. If the smoothness is less than 10 seconds, it is necessary to lower the intrinsic viscosity of the polyester resin (A) in order to adhere to the paper. Therefore, the necking phenomenon of the film from the T die to the laminate on the paper surface is large. This is not preferable because the production yield may decrease. Moreover, the weight of paper is 10-500 g / m < ² > normally, Preferably it is 15-400 g / m < ² >, More preferably, it is 20-300 g / m < ² >.

  The polyester laminated paper according to the present invention is obtained by laminating the above-mentioned polyester resins (A) and (B) formed into a thin film on the paper in this order, and laminating and laminating on at least one surface. Including those laminated on the surface. By laminating, functions such as releasability, heat resistance, water resistance, and oil resistance can be imparted to the paper. The surface of the paper on which the polyester resin is not laminated may be as it is, or a polyester resin composition, a film or sheet made of another resin, or a laminate of these may be laminated. Other resin films or sheets may be pre-colored or printed with characters, patterns, pictures, and the like. When a picture or the like is printed on another resin film or sheet and a polyester layer is formed on this surface, the picture is not exposed on the surface, and a laminated paper having a beautiful appearance can be obtained. Other resin films or sheets include thermoplastic resins other than polyester resins, aluminum foil, and the like, and may be foams.

In the present invention, when the above-described polyester resins (A) and (B) are laminated on the paper, the film thickness ratio of each resin after lamination [d (resin B) / d (resin A)] ( Hereinafter, the respective resins are laminated so that the film thickness ratio is d (B) / d (A)) is 0.5 to 50. Thereby, the laminated paper excellent in all of extrudability, container workability, and adhesiveness can be obtained. When d (B) / d (A) is less than 0.5, necking increases, and the lamination speed tends to decrease. On the other hand, when it exceeds 50, adhesion and container processability tend to decrease. is there. The film thickness ratio described above can be set in the range of 0.5 to 50 by adjusting the extrusion amounts of the two extruders in the co-extrusion conditions described later.
The above-mentioned film thickness ratio d (B) / d (A) has a lower limit of 1.0 or more, in that a laminated paper excellent in any of extrudability, container processability, and adhesion can be obtained. Is preferably 2.0 or more, particularly 3.0 or more, and the upper limit is preferably 30 or less, more preferably 20 or less, further 10 or less, and particularly preferably 8 or less.

  In the present invention, the thickness of the entire polyester laminate film after laminating the polyester resin layers (A) and (B) is not particularly limited, but is usually 1 to 100 μm, preferably 5 to 50 μm, particularly 10 to 25 μm. is there. If it is less than 1 μm, defects such as pinholes are likely to occur during molding, and if it exceeds 100 μm, the container processability tends to decrease.

The method for forming the polyester laminated paper of the present invention is not particularly limited, and various known methods can be employed. As a specific example, a melt-laminated film obtained by melting and kneading sufficiently dried chip-like polyester resins (A) and (B) in separate extruders and joining them with a feed block type laminating die through a conduit, for example. A paper laminated with a polyester resin can be obtained by continuously co-extruding onto a base paper, winding with cooling and pressing with a chill roll.
The air gap during coextrusion is usually 15 cm or less, preferably 10 cm or less, and more preferably 8 cm or less. When it exceeds 15 cm, the temperature of the molten film is lowered before being laminated, and the adhesion to paper tends to be remarkably lowered.

The extrusion temperature of the polyester resins (A) and (B) when molding the polyester laminated paper is usually 230 to 320 ° C., preferably 240 to 310 ° C., more preferably 250 to 305 ° C., and 255. -300 degreeC is still more preferable, and 260-295 degreeC is especially preferable. If the resin temperature exceeds 320 ° C, the necking-in phenomenon and ear harshness will increase due to thermal decomposition, and high-speed extrusion of polyester will become difficult, and the amount of trimming will tend to decrease and the extrudability will tend to decrease. The laminated polyester tends to turn yellow, and the odor retention and taste retention tend to be insufficient. The chill roll temperature is usually 20 ° C. or higher, preferably 30 ° C. or higher, more preferably 40 ° C. or higher.
In the present invention, a gas barrier resin layer such as nylon or EVOH (ethylene-vinyl alcohol copolymer) is bonded between the layer made of the polyester resin (A) and the layer made of the polyester resin (B). By coextrusion through the layers, a laminated paper having good gas barrier properties can also be produced.

  The polyester laminated paper of the present invention thus obtained is suitable for a paper container as a resin material having excellent adhesion, heat resistance and moldability, and is used for storage of foods containing moisture and oil, or frozen foods. It can be suitably used for paper containers for foods that require heat resistance at high temperatures such as microwave oven heating and microwave oven heating of refrigerated foods.

  When the laminated paper container of the present invention is cut into an appropriate size by laminating the above-mentioned polyester laminated paper and stacked in a flat plate shape, one or many sheets are transferred to a molding die at one time, or When it is wound into a roll, it is obtained by transferring to a molding die while rewinding and thermoforming. The thermoforming method may be a conventionally known method, and examples thereof include a vacuum forming method, a pressure forming method, and a press forming method. The temperature at the time of thermoforming is usually 90 to 160 ° C, preferably 100 to 150 ° C, more preferably 110 to 140 ° C.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these examples, unless the summary is exceeded. In addition, the physical-property measuring method of the polyester resin to laminate, the characteristic evaluation method of the polyester laminated paper, and the manufacturing method of the polyester resin are as follows.

[Method for measuring physical properties of polyester resin]
(1) Thermal characteristics About 10 mg of a polyester resin sample was shaved, and a DSC manufactured by Seiko Instruments Inc. (differential scanning calorimeter “DSC220U type”) was used. The temperature was raised and lowered at a speed of ± 20 ° C./min in the range of 300 ° C., and the melting point (Tm) ° C. and the falling crystallization temperature (Tc) ° C. of the polyester resin were measured.
(2) Intrinsic viscosity After the raw material polyester is dried with hot air at 120 ° C. for about 6 hours, a mixed solvent of phenol / 1,1,2,2-tetrachloroethane = 50/50 (weight ratio) using an Ubbelohde viscometer. (30 ° C.) was used to measure the intrinsic viscosity [η] (dl / g).

(3) Ti atom content The titanium catalyst metal concentration (weight ratio) in the polyester resin was quantified by Induced Coupled Plasma (ICP).
(4) Melt tension and melt viscosity After drying the polyester resin at 120 ° C. for about 6 hours, the melt tension (mN) at a cylinder temperature of 250 ° C. was measured with a Toyo Seiki Co., Ltd. Capillograph. The take-up speed was 20 m / min, the capillary diameter / length = 0.5 mm / 5 mm was used, and the piston speed was 5 mm / min. After putting 10 g of pellets into the cylinder, it was melted over 5 minutes, and the average value at 6-7 minutes was adopted as the melt tension.

On the other hand, the melt viscosity was measured by measuring the melt viscosity (Pa · S) of the dried raw material polyester at a cylinder temperature of 250 ° C. with a Toyo Seiki Co., Ltd. Capillograph. The take-up speed was 20 m / min, and the capillary diameter / length = 1.0 mm / 30 mm was used. After charging 20 g of pellets in the cylinder, the pellet was melted for 3 minutes, and the melt viscosity at a shear rate of 91.2 (sec ⁻¹ ) was adopted.

[Characteristic evaluation method of polyester laminated paper]
(1) Laminate Layer Thickness Laminate paper is cut at three locations on both ends and the center in the width direction, and the cross section is scanned using a scanning electron microscope (manufactured by Hitachi, Ltd., model: S-2500). The photograph was taken at a magnification of 1000 times. The portion of the thin-film polybutylene terephthalate resin composition shown in this enlarged photograph was measured using a JIS grade 1 metal ruler, and the average value of the measurement results at three locations was taken as the thickness (μm) of the laminate layer. Calculated.
(2) Evaluation of extrudability The die width value is (W (A)), the average value obtained by measuring 10 points of the PBT width laminated on paper at intervals of 1 m in the extrusion direction (W (B)), and the film thickness in the vicinity of both ends. Neck-in amount (%), trimming amount (%) and width of cut (%) are calculated by the following formulas, where the total length in the PBT width direction of the part where the diameter exceeds 18 microns is (W (C)). The fastest line speed that is 10% or less was defined as the extrusion lamination speed in the table. Extrudability was evaluated when the extrusion laminating speed exceeded 190 m / min, ◎, 130-190 m / min, ○, and less than 130 m / min.
Neck-in amount (%) = {[W (A) −W (B)] / W (A)} × 100
Trimming amount (%) = [W (C) / W (B)] × 100
Clearance amount (%) = {[W (B) −W (C)] / W (A)} × 100

(3) Adhesion evaluation When extrusion laminating a polyester resin to a paper base material, a piece of 200 mm square aluminum foil is inserted between the paper and the molten polyester so that one piece is perpendicular to the MD direction (extrusion direction). A laminate sample having a portion where polyester and paper were not in close contact was obtained. Next, the laminate sample was cut into a strip shape having a width of 15 mm and a length of 150 mm. The strip sample was composed of a close contact portion of 75 mm and a non-contact portion of 75 mm. Each of the polyester end and the paper end of the non-adhered portion is sandwiched between chucks of a tensile tester, and 200 mm / min. The polyester film and the paper were evaluated for adhesion according to the following criteria. Incidentally, the test (the number of samples was n = 10).
○: In the test using the tensile tester, the polyester film was ductile broken in all ten test pieces, and the film was similarly ductile broken even when the polyester edge and paper edge were pulled strongly by hand.
X: Peeling of 5 mm or more between the polyester film and the paper was observed with one or more test pieces during the test by the tensile tester.

(4) Color tone evaluation The color tone of the polyester laminated paper was visually evaluated according to the following criteria.
A: Level almost unchanged compared to the white of paperboard.
○: There is a slight yellow change compared to the white of paper.
(Triangle | delta): The amount of yellowing is large compared with the original white of paper.
(5) Container processability evaluation 30 pieces of polyester laminated paper were put in a hot press machine having a male and female mold of a box type (D × W × H = 30 × 180 × 200 mm), and molded at 130 ° C. for 3 seconds. processed. Workability was evaluated according to the following criteria. In addition, 10 tests (test number n = 10) were created under the same conditions, and the evaluation was performed by visual evaluation.
○: There is no change in the appearance of the paper container after molding.
X: After molding, the polyester film and paper were partially separated.

[Production method of polyester resins (A) and (B)]
Both raw materials were supplied to a slurry preparation tank at a ratio of 1.8 mol of 1,4-butanediol to 1 mol of terephthalic acid, and the slurry prepared by mixing with a stirrer was at a temperature of 230 ° C. and a pressure of 78.7 kPa ( 590 mmHg) and continuously supplied to the esterification reaction tank, tetra-n-butyl titanate (50 ppm or 200 ppm in the PBT yield) is continuously supplied as a catalyst. The esterification reaction was carried out for 3 hours to obtain an oligomer having an esterification reaction rate of 97.5%.

  The oligomer obtained by the esterification reaction is continuously supplied to a first polycondensation reaction tank adjusted to a temperature of 250 ° C. and a pressure of 2.66 kPa (20 mmHg), and subjected to a polycondensation reaction with a residence time of 2 hours under stirring by a stirrer. To obtain a prepolymer having an intrinsic viscosity of 0.250 dl / g. The prepolymer was continuously supplied to a second polycondensation reaction tank adjusted to a temperature of 250 ° C. and a pressure of 0.133 kPa (1 mmHg), and subjected to polycondensation with a residence time of 2.5 to 5.5 hours under stirring by a stirrer. The reaction was further advanced. Next, the polymer was extracted and transferred to a die, and the polymer was extruded from the die into a cylindrical shape. After cooling with cooling water at 20 ° C. for 0.9 seconds, the polymer was cut with a cutter, and the intrinsic viscosity [η] = 0.85−1. .44 polybutylene terephthalate granular pellets were obtained. The obtained polyester resins (A) and (B) had the physical properties shown in Tables 1 and 2.

[Examples 1 to 4 and Comparative Examples 1 to 5]
The pellets of each polyester (PBT) resin (A) and (B) listed in Table 1 and Table 2 below were each dried at 120 ° C. for 6 hours in a hot air dryer. Next, the PBT resin (A) was put into a hopper of a 60 mm single screw extruder, and the PBT resin (B) was put into a hopper of a 120 mm single screw extruder, and each of the melt-kneaded resins (A) and ( B) are joined with a feed block type laminated T-die (lip width 1500 mm, air gap 70 mm, lip gap 1.0 mm) through a conduit, both of which have a resin temperature of 290 ° C. and continuously melt the laminated film on paper. Extruded. The co-extruded laminated film was cooled with a tyrol controlled at 30 ° C. together with the paper and wound up while being pressed to produce a laminated paper having the thicknesses shown in Tables 1 and 2.

In Comparative Example 3, the connection of the conduit was changed, and PBT resin (B) was charged into a 60 mm single screw extruder, and PBT resin (A) was charged into a 120 mm single screw extruder.
The paper used here is paper with a smoothness of 30 seconds and 35 g / m ² . A box-shaped container was prepared from the obtained laminated paper using a 130 ° C. hot press molding machine, and various evaluations were performed. The results are shown in Tables 1 and 2.

(1) From Examples 1 to 4 in Table 1, a PBT resin (A) having a melt viscosity of 500 (Pa · S) or less and a PBT resin (B) having a melt tension of 1.0 mN or more are compared with a film thickness ratio d. It can be seen that when laminated so that (B) / d (A) is in the range of 0.5 to 50, a laminated paper excellent in all of extrudability, adhesion, container processability, and color tone can be obtained. .
(2) When comparing Examples 1 to 4 in Table 1 and Comparative Example 1 in Table 2, when the melt tension of the PBT resin (B) is below 1.0 mN, the extrusion laminating speed is slow, the extrudability and the container It turns out that workability is inferior.
(3) Comparing Example 1 in Table 1 and Comparative Examples 2 and 5 in Table 2, when the melt viscosity of the PBT resin (A) exceeds 500 (Pa.S), the paper and the polyester resin layer It can be seen that the adhesion of the container is poor and the processability of the container is also poor.
(4) Comparing Example 1 in Table 1 and Comparative Examples 3 and 4 in Table 2, when the film thickness ratio d (B) / d (A) is lower than 0.5, the extrusion laminating speed is slow and the extrudability is low. In addition, when the film thickness ratio d (B) / d (A) exceeds 50, it can be seen that the adhesion and container processability are inferior.
(5) Comparing Example 1 in Table 1 with Comparative Example 5 in Table 2, when the titanium atom content in the PBT resin (B) greatly exceeds 100 ppm, the extrudability is poor and the yellowing amount of the paper is large. It turns out that there is a tendency to become.

Claims (5)

In a method for producing a laminated polyester laminated paper in which at least two kinds of polyester resins mainly composed of a butylene terephthalate repeating unit are laminated on at least one surface of paper by coextrusion, the polyester resin (A ), A resin having a melt viscosity of 500 (Pa · S) or less at 250 ° C. and a shear rate of 91.2 (sec ⁻¹ ) is used on the layer containing the resin (A) on the side opposite to the paper As the polyester resin (B) to be laminated, a resin having a melt tension at 250 ° C. of 1.0 mN or more is used, and the film thickness ratio d (resin B) / d (resin A) after lamination is 0.5 to 50. Thus, the manufacturing method of the laminated polyester laminated paper characterized by laminating each said resin (A) and (B).   The method for producing a laminated polyester laminated paper according to claim 1, wherein the polyester resin (B) contains 10 to 100 ppm (weight ratio) of titanium atoms. The method for producing a laminated polyester laminated paper according to claim 1 or 2, wherein the smoothness of the paper (by a measurement method based on JIS P8119) is 10 seconds or more.   A laminated polyester laminated paper produced by the method according to claim 1.   A container made of polyester laminated paper, which is obtained by molding the laminated polyester laminated paper according to claim 4.