JP4791208B2 - Method for producing stretched thermoplastic polyester resin sheet - Google Patents

Description

  The present invention relates to a method for producing a stretched thermoplastic polyester resin sheet, and more particularly to a method for producing a stretched thermoplastic polyester resin sheet having excellent tensile strength, tensile elastic modulus, and heat resistance.

Conventionally, a method for producing a transparent crystalline polymer sheet having a smooth surface and a high strength and elastic modulus by pultrusion has been studied. For example, crystals such as polyethylene, polypropylene, polyacetal resin, nylon, etc. The temperature of the base sheet of the differential polymer calorimetry melting curve is not exceeded the deformation starting temperature when the sheet is heated at a rate of temperature increase of 1 ° C./min with a 10 MPa load applied to the sheet. There has been proposed a method for producing a crystalline polymer sheet, which is drawn through at least a draw ratio of 2.5 times or more through a pair of heated rollers (see, for example, Patent Document 1).
JP 60-15120 A

  However, in order to stretch a polyester resin by the above method for producing a crystalline polymer sheet, the polyester resin is too hard at low temperatures and lacks flexibility necessary for stretching, and relaxation of orientation becomes dominant at high temperatures. Therefore, in order to obtain a stretched sheet having excellent strength and elastic modulus, it is necessary to perform pultrusion molding within the temperature range of the glass transition temperature of the polyester resin -20 ° C to the glass transition temperature + 20 ° C. The system resin sheet has a drawback in that the elastic modulus rapidly decreases when heated to a temperature higher than the glass transition temperature.

  An object of the present invention is to provide a method for producing a stretched thermoplastic polyester resin sheet excellent in tensile strength, tensile elastic modulus, and heat resistance in view of the above-mentioned drawbacks.

  The method for producing a stretched thermoplastic polyester resin sheet according to the present invention is obtained by converting an amorphous thermoplastic polyester resin sheet from a glass transition temperature of the thermoplastic polyester resin to -20 ° C. to a glass transition of the thermoplastic polyester resin. Thermoplasticity in a differential scanning calorimetry curve measured by drawing through a pair of rolls at a temperature of + 20 ° C. and drawing and drawing, then uniaxially drawing at a temperature higher than the temperature of the roll, and then measured at a heating rate of 10 ° C./min It is characterized by being heat-set at a temperature higher than the rising temperature of the crystallization peak of the polyester resin and lower than the uniaxial stretching temperature.

  Examples of the thermoplastic polyester resin used in the present invention include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyglycolic acid, poly (L-lactic acid), poly (3-hydroxybutyrate), poly ( 3-hydroxybutyrate / hydroxyvalerate), poly (ε-caprolactone), polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polybutylene succinate / lactic acid, polybutylene succinate / carbonate, polybutylene succinate Nate / terephthalate, polybutylene adipate / terephthalate, polytetramethylenadipate / terephthalate, polybutylene succinate / adipate / terephthalate, etc. Polyethylene terephthalate is preferable.

  The stretched thermoplastic polyester resin sheet is in an amorphous state. The stretched thermoplastic polyester resin sheet may be in an amorphous state, and its crystallinity is not particularly limited, but the crystallinity measured with a differential scanning calorimeter is preferably less than 10%, more Preferably it is less than 5%.

  Although the thickness of a thermoplastic polyester-type resin sheet is not specifically limited, 0.5-5 mm is preferable. If it is less than 0.5 mm, the thickness of the sheet after stretching becomes too thin, and the strength during handling may not be sufficient, and if it exceeds 5 mm, stretching may be difficult.

  In the present invention, the stretched thermoplastic polyester resin sheet in the amorphous state is drawn through a pair of rolls and drawn and stretched.

  If the temperature of the pair of rolls at the time of drawing and drawing is low, the thermoplastic polyester resin sheet is too hard and may be cut first even if it is drawn. The thermoplastic polyester resin sheet becomes soft when the temperature is high, and the thermoplastic polyester resin sheet is cut by the tension that pulls out the sheet. The glass transition temperature is −20 ° C. to the glass transition temperature of the thermoplastic polyester resin + 20 ° C., preferably the glass transition temperature of the thermoplastic polyester resin to the glass transition temperature of the thermoplastic polyester resin + 10 ° C. Temperature range.

  In addition, when the amorphous polyester resin sheet in an amorphous state is pulled out, the roll does not necessarily rotate. However, particularly when the thermoplastic polyester resin sheet is thick, heat accumulation of the roll due to shearing heat generation occurs. It is preferable to rotate the sheet in the drawing direction because the temperature of the resulting sheet is likely to increase.

  When the rotation speed of the roll is slow, the contact time between the roll and the thermoplastic polyester resin sheet becomes longer, frictional heat is generated, the roll temperature rises, and the effect of cooling the heated thermoplastic polyester resin is reduced. However, when the predetermined drawing and stretching temperature is exceeded and the rotational speed of the roll is increased, only the thermoplastic polyester resin on the surface of the thermoplastic polyester resin sheet flows and cannot be drawn and drawn uniformly. Further, the elastic modulus of the drawn and drawn thermoplastic polyester resin sheet is lowered.

  The draw ratio of the above-described drawing stretching is not particularly limited. However, if the stretching ratio is low, a sheet excellent in tensile strength and tensile elastic modulus cannot be obtained. If the stretching ratio is high, the sheet tends to break during stretching. 2-9 times is preferable, More preferably, it is 4-8 times.

  In the present invention, the drawn and stretched thermoplastic polyester resin sheet is uniaxially stretched at a temperature higher than the temperature of the roll.

  The polyester resin of the drawn stretched thermoplastic polyester resin sheet that has been drawn and drawn has high strength because the molecular chains are highly oriented with isotropic crystallization and orientation suppressed by heat, which is a hindrance to stretching. Although the elastic modulus is excellent, the degree of crystallinity is low. Therefore, when heated, the orientation is easily relaxed and the elastic modulus is lowered.

  However, the stretched thermoplastic polyester resin sheet that has been drawn and stretched is uniaxially stretched at a temperature higher than that of the roll, so that the degree of crystallinity is increased without relaxation and the orientation is easy even when heated. Thus, a stretched sheet having excellent heat resistance that is not relaxed can be obtained.

  As the uniaxial stretching method, a roll stretching method is preferably used. The roll stretching method is a method in which a stretched raw fabric is sandwiched between two pairs of rolls having different speeds, and the stretched raw fabric is pulled while being heated, and the molecular orientation can be strongly oriented only in a uniaxial direction. In this case, the speed ratio of the two pairs of rolls becomes the draw ratio.

  The temperature at the time of the uniaxial stretching may be higher than the temperature of the pair of rolls at the time of drawing and drawing, but if it is too high, the drawn and stretched thermoplastic polyester resin sheet is melted and cut. A temperature range from the rising temperature of the crystallization peak of the thermoplastic polyester resin to the rising temperature of the melting peak in the differential scanning calorimetry curve measured at a heating rate of 10 ° C./min is preferable.

  The rising temperature of the crystallization peak of polyethylene terephthalate is about 120 ° C., and the rising temperature of the melting peak is about 230 ° C. Accordingly, when the polyethylene terephthalate sheet is uniaxially stretched, it is preferably uniaxially stretched at about 120 ° C to about 230 ° C.

  The stretching ratio of the uniaxial stretching is not particularly limited, but if the stretching ratio is low, a sheet excellent in tensile strength and tensile elastic modulus cannot be obtained. If the stretching ratio is high, the sheet tends to break during stretching. 1.05 to 3 times, and more preferably 1.1 to 2 times. In addition, the total draw ratio of the drawing and uniaxial stretching is preferably 2.5 to 10 times for the same reason.

  In the present invention, a stretched thermoplastic polyester resin sheet that has been uniaxially stretched is heat-set in order to improve heat resistance.

  When the heat setting temperature is higher than the uniaxial stretching temperature, the thermoplastic polyester resin dissolves, the stretching (orientation) disappears, the tensile elastic modulus, the tensile strength, etc. decrease, and the differential scanning measured at a heating rate of 10 ° C./min. If the temperature is lower than the rising temperature of the crystallization peak of the thermoplastic polyester resin in the calorimetric curve, the crystallization of the thermoplastic polyester resin does not proceed and the heat resistance does not improve. Therefore, the differential scanning calorific value measured at a heating rate of 10 ° C./min. The temperature is not less than the rising temperature of the crystallization peak of the thermoplastic polyester resin on the curve and not more than the uniaxial stretching temperature.

When heat is drawn and is under great tension oriented thermoplastic polyester resin sheet, or not under tension, since a very small state contracts, oriented thermoplastic length of the polyester resin sheet Is preferably carried out in a state where no change occurs, and it is preferable that no pressure is applied to the stretched thermoplastic polyester resin sheet.

  That is, it is preferable to heat-set so that the length of the stretched thermoplastic polyester resin sheet that has been heat-set is 0.95 to 1.1 of the length of the stretched thermoplastic polyester-based resin sheet before heat setting. .

  Therefore, when the stretched thermoplastic polyester resin sheet is heat-set continuously while moving in the heating chamber with a roll such as a pinch roll, the feed rate ratio of the stretched thermoplastic polyester resin sheet on the inlet side and the outlet side is set to 0. It is preferable that the temperature is set to be .95 to 1.1 and heat fixed.

  The heating method at the time of heat setting is not particularly limited, and examples thereof include a method of heating with hot air or a heater.

  The time for heat setting is not particularly limited, but is generally 10 seconds to 10 minutes, although it varies depending on the thickness of the stretched thermoplastic polyester resin sheet and the heat setting temperature.

Furthermore, the range of the rising temperature of the crystallization peak of the thermoplastic polyester resin in the differential scanning calorimetry curve of the heat-set stretched thermoplastic polyester resin sheet measured at a glass transition temperature to a heating rate of 10 ° C./min. Thus, it is preferable to anneal in a state where no tension is applied.

  By annealing, the stretched thermoplastic polyester resin sheet has good mechanical properties such as elastic modulus, and even if it is heated to a temperature higher than the glass transition temperature, the mechanical properties such as elastic modulus may decrease. And the shrinkage rate can be kept low.

In addition, since the stretched thermoplastic polyester resin sheet is stretched when a large tension is applied, it is preferable to anneal the stretched thermoplastic polyester resin sheet in a state where no tension is applied.

  That is, it is preferable to anneal so that the length of the annealed stretched thermoplastic polyester resin sheet is 1.0 or less of the length of the stretched thermoplastic polyester resin sheet before annealing.

  Therefore, when the stretched thermoplastic polyester resin sheet is continuously annealed while being moved in a heating chamber by a roll such as a pinch roll, the feed rate ratio of the stretched thermoplastic polyester resin sheet on the inlet side and the outlet side is set to 1. It is preferable to anneal by setting it to be 0 or less.

  The heating method at the time of annealing is not particularly limited, and examples thereof include a method of heating with hot air or a heater.

  The time for annealing is not particularly limited and varies depending on the thickness of the stretched thermoplastic polyester resin sheet and the annealing temperature, but is generally preferably 10 seconds or more, more preferably 30 seconds to 5 minutes, and still more preferably 1-2. Minutes.

  The structure of the manufacturing method of the extending | stretching thermoplastic polyester-type resin sheet of this invention is as the above-mentioned, and the extending | stretching thermoplastic polyester-type resin sheet obtained is excellent in tensile strength, a tensile elasticity modulus, and heat resistance.

  Next, examples of the present invention will be described, but the present invention is not limited to the following examples.

Example 1
A polyethylene terephthalate sheet (made by Teijin Chemicals, trade name “A-PET sheet FR”) having a thickness of 1 mm and a width of 200 mm is supplied to a stretching apparatus (manufactured by Kyowa Engineering Co., Ltd.), preheated to 75 ° C., and then heated to 80 ° C. Then, the surface of the polyethylene terephthalate sheet is drawn and drawn at a speed of 2 m / min between a pair of rolls (roll interval 0.2 mm) rotating in the drawing direction at 0.05 m / min, and then in a hot air heating tank. The temperature is set to 170 ° C., the outlet speed is set to 2.5 m / min, and the roll is uniaxially stretched about 6 times. Further, the pair of rolls are made equal to each other before and after the uniaxially stretched polyethylene terephthalate sheet, and the rotation speed is made equal. The length of the stretched polyethylene terephthalate sheet is not changed, and 150 ° C hot air is blown on both sides for 3 minutes to fix the heat. Draw ratio to obtain about 6 times stretched polyethylene terephthalate sheet.

  The polyethylene terephthalate sheet has a glass transition temperature of 72 ° C., a rising temperature of the crystallization peak in the differential scanning calorimetry curve measured at a heating rate of 10 ° C./min is about 118 ° C., and a rising temperature of the melting peak is about It was 230 ° C.

(Comparative Example 1)
A polyethylene terephthalate sheet (made by Teijin Chemicals, trade name “A-PET sheet FR”) having a thickness of 1 mm and a width of 200 mm is supplied to a stretching apparatus (manufactured by Kyowa Engineering Co., Ltd.), preheated to 75 ° C., and then heated to 80 ° C. Then, the surface of the polyethylene terephthalate sheet is drawn and drawn at a speed of 2 m / min between a pair of rolls (roll interval 0.2 mm) rotating in the drawing direction at 0.05 m / min, and then in a hot air heating tank. The temperature is set to 170 ° C., the outlet speed is set to 2.5 m / min, and the film is stretched about 6 times. Further, the front and back of the uniaxially stretched polyethylene terephthalate sheet are respectively paired with the same number of rotations, The length of the stretched polyethylene terephthalate sheet is kept unchanged, and hot air of 115 ° C. is blown on both sides for 3 minutes to heat-fix, Magnification to obtain about 6 times stretched polyethylene terephthalate sheet.

  The physical properties of the obtained stretched polyethylene terephthalate sheet were evaluated by the following evaluation methods, and Tables 1 and 2 show the results.

(1) Tensile strength, tensile modulus Measured according to the tensile test method of JIS K 7113.

(2) Heat resistance The obtained stretched polyethylene terephthalate sheet was placed on an iron plate heated to a predetermined temperature shown in Table 2, heated for 3 minutes, and then tensile elastic according to the tensile test method of JIS K 7113. The rate was measured.

Claims (2)

  The amorphous polyester resin sheet in an amorphous state is drawn through a pair of rolls having a glass transition temperature of −20 ° C. to a glass transition temperature of the thermoplastic polyester resin + 20 ° C. After that, it is uniaxially stretched at a temperature higher than the temperature of the roll, and is equal to or higher than the rising temperature of the crystallization peak of the thermoplastic polyester resin in the differential scanning calorimetry curve measured at a heating rate of 10 ° C./min, A method for producing a stretched thermoplastic polyester resin sheet, characterized by heat-setting at a temperature lower than a uniaxial stretching temperature.  The method for producing a stretched thermoplastic polyester resin sheet according to claim 1, wherein the amorphous polyester resin sheet in an amorphous state has a crystallinity of less than 10% as measured by a differential scanning calorimeter.