JPWO2007083720A1 - Polyester foam sheet and method for producing the same - Google Patents

Abstract

The present invention includes air bubbles having 50 to 100% by weight of polytrimethylene terephthalate, an apparent density of 0.05 to 1.25 g / cm 3, and an average air bubble size of 0.01 to 50 μm, and A polyester foam sheet having a ratio (S / T) of an average size (S) in the plane direction of bubbles to an average size (T) in the thickness direction of 0.05 to 10 and a method for producing the same are provided.

Description

  The present invention relates to a polyester foam sheet comprising polytrimethylene terephthalate as a main component, a method for producing the same, and a light reflector made of the polyester foam sheet. More specifically, a polyester foam sheet mainly composed of polytrimethylene terephthalate having excellent light reflectivity, flexibility, heat insulation, and lightness by having fine bubbles inside, a method for producing the same, and the foaming The present invention relates to a light reflector made of a sheet.

  Thermoplastic polyester resins represented by polyethylene terephthalate (hereinafter abbreviated as “PET”) resin and polybutylene terephthalate (hereinafter abbreviated as “PBT”) resin have excellent heat resistance, chemical resistance, weather resistance and mechanical properties. It is widely used in the field of fibers and molded articles by taking advantage of such features. In particular, extruded products such as films and sheets have excellent characteristics in terms of chemical resistance, weather resistance, mechanical properties, etc., and are various in food, daily packaging containers, packaging materials, building materials, light reflectors, etc. It is expected as a material for applications.

  In these applications, in order to improve flexibility, heat insulation, light weight, and to provide an excellent light reflection function, a sheet or film containing very fine bubbles of several tens of μm or less inside is strong. It has come to be desired.

  Conventionally, as a foamed polyester sheet containing fine bubbles inside, a polyethylene terephthalate (PET) resin and an incompatible resin are finely dispersed to form a film and then stretched uniaxially or biaxially. There is known a polyester film in which fine cavities having an incompatible resin as a core are formed (see, for example, Patent Document 1).

  In addition, the PET sheet roll has fine bubbles with an average bubble diameter of 50 μm or less obtained by impregnating carbon dioxide in a high-pressure container and then heating to 240 ° C. to foam the permeated gas. There is also a proposal of a thermoplastic polyester foam having a thickness of 200 μm or more and a specific gravity of 0.7 or less (see, for example, Patent Document 2).

  As a similar technique, a technique using a polytrimethylene terephthalate (hereinafter abbreviated as “PTT”) resin capable of obtaining a fiber excellent in elastic recovery has been proposed (for example, see Patent Document 3).

  The technology that can improve the problem of poor processability and the drawbacks of bubbles being easily crushed or being easily creased or scratched is as follows. After injecting carbon dioxide into molten thermoplastic resin, Among the components constituting the film, having a specific bubble obtained by cooling a sheet of foamed carbon dioxide gas simultaneously formed into a sheet shape at the part, cooled on a cast drum, and then stretched and heat-treated There is a proposal of a white film characterized in that 95% or more is made of one kind of thermoplastic resin and is stretched at least uniaxially (see, for example, Patent Document 4).

Further, 30% by weight or more is a trimethylene terephthalate unit, and an apparent density composed of a trimethylene terephthalate polymer having a specific intrinsic viscosity and a terminal carboxylic acid amount is 0.001 g / cm ^{3 to} 1.2 g / cm. There is also a proposal of a foam that is ³ (see, for example, Patent Document 5).

  On the other hand, a foamed polyester sheet containing fine bubbles inside is considered to be used for a light box of a liquid crystal display device, a lighting device such as a fluorescent lamp, etc. by taking advantage of high light reflectance and high diffuse reflectance. ing. As such a light reflecting plate, an average bubble diameter of 50 μm or less was obtained by allowing a PET sheet roll to infiltrate carbon dioxide in a high-pressure vessel and then heating to 240 ° C. to foam the infiltrated gas. There is a proposal of a light reflecting plate made of a thermoplastic polyester foam having a fine bubble of 200 μm or more and a specific gravity of 0.7 or less (for example, see Patent Document 2).

Also, a foam sheet or film having a specific apparent specific gravity and a specific void content obtained by stretching a resin containing polymethylpentene that is incompatible with PET and used as a light reflector. There is also a proposal (see, for example, Patent Document 6).
Japanese Patent No. 3018539 Japanese Patent No. 2925745 Japanese Patent Laid-Open No. 11-268212 JP-A-11-300814 JP 2002-226619 A JP 2005-281396 A

  However, in the above-mentioned foamed film of Patent Document 1, since bubbles are formed by stretching in the film forming process, the film has a problem that orientation crystallization is progressing, elongation is low, and workability is poor. is doing. In addition, the foamed film has a structure in which resin is laminated in the film surface direction and has air bubbles such as gaps, so that the air bubbles are easily crushed when bent or when force is applied from the surface direction. Also, there is a drawback that creases and scratches are easily attached. Furthermore, only a thin film that can be stretched can be obtained, and it is difficult to stand as a molded body.

  According to the study by the present inventors, the sheet obtained by the technique of Patent Document 2 is inferior in flexibility and formability. Moreover, even if the technology is applied to polytrimethylene terephthalate (PTT) as it is, the sheet crystallizes and does not foam when infiltrated with gas, so that a sheet having good flexibility and formability can be obtained. Not only can not be obtained, it is not even possible to obtain a sheet having a fine foam.

  In the technique of Patent Document 3, a void-forming thermoplastic resin and / or bubble-forming inorganic fine particles that are incompatible with polytrimethylene terephthalate (PTT) resin are mixed, and the resin interface or inorganic is formed in the film stretching step. Bubbles are formed at the interface with the fine particles. However, according to the study by the present inventors, although the flexibility is somewhat increased by using a PTT resin having a low crystal elastic modulus, the film remains oriented and crystallized or has bubbles such as gaps. Therefore, the effect is not sufficient, and it is still difficult to obtain a thick film. As described above, even when the technique of Patent Document 3 is used, the problem that occurs when the polyethylene terephthalate (PET) resin described above is used cannot be solved.

  In the techniques of Patent Documents 4 and 5, volatile foaming agent of 1% by weight or more with respect to the resin, specifically, 20% by weight of carbon dioxide or 4% by weight of n-butane is injected and dissolved to obtain a foam. It has gained. However, according to the study by the present inventors, although the foam is obtained by these techniques, the bubbles cannot be miniaturized, and the above-described problem cannot be solved.

As described above, the conventional techniques have a problem that it is impossible to obtain a foam sheet having excellent flexibility, heat insulation, light weight, and light reflectivity.
On the other hand, when considered as a light reflecting plate, since the technique of Patent Document 2 uses PET, it is inferior in flexibility and difficult to process into a shape corresponding to the light source, or inferior in elastic recovery. For this reason, there are problems such as bending or wrinkling when trying to process the curved surface according to the light source.

  In addition, since the sheet obtained by the technique of Patent Document 6 has a high reflectance even if it is thin, it can be easily deformed by reducing the thickness, but the contained cavity is stretched. Therefore, if the curvature at the time of processing into a curved surface is reduced, it is easily bent at an acute angle or wrinkles frequently occur.

  As described above, the conventional technology has a problem that it is not possible to obtain a light reflecting plate that can be easily processed into a shape suitable for various light sources and can form a wide shape such as a curved surface with a small curvature. there were.

  The present invention solves the above-mentioned problems, the purpose of which is excellent in light reflectivity, flexibility, heat insulation, lightweight, a polyester foam sheet based on polytrimethylene terephthalate and a method for producing the same, Another object of the present invention is to provide a light reflecting plate which is made of the foamed sheet and has excellent light reflectivity and can be easily processed without wrinkles into a shape suitable for a light source.

As a result of diligent research to solve the above problems, the inventors of the present invention consisted of a resin composition mainly composed of polytrimethylene terephthalate (PTT), and an ultrafine foamed sheet having fine bubbles of a specific shape inside, As a result, the inventors have found that the above problems can be solved, and have completed the present invention. That is, the object of the present invention has been achieved by the following polyester foam sheet and its production method.
(1) Polyester foam sheet, containing 50 to 100% by weight of polytrimethylene terephthalate, an apparent density of 0.05 to 1.25 g / cm ³ , and an average cell size of 0.01 to 50 μm A polyester foam sheet containing bubbles and having a ratio (S / T) of an average size (S) in the plane direction of the bubbles to an average size (T) in the thickness direction of 0.05 to 10.
(2) The polyester foam sheet according to (1), wherein the thickness of the polyester foam sheet is 1 μm to 10 mm.
(3) The average bubble size of the bubbles is 0.01 to 30 μm, and the ratio (S / T) between the average size (S) in the plane direction of the bubbles and the average size (T) in the thickness direction is 0. The polyester foam sheet according to (1) or (2), which is 7 to 3.
(4) The polyester foam sheet according to any one of (1) to (3), wherein the polyester foam sheet has a thermal shrinkage rate at 150 ° C. of −2 to 5%.
(5) The polyester foam sheet according to any one of (1) to (4), wherein an average light reflectance of the polyester foam sheet with respect to light having a wavelength of 400 to 700 nm is 80% or more.
(6) The polyester foam sheet according to any one of (1) to (5), which is produced by a melt extrusion method.
(7) The polyester foam sheet according to any one of (1) to (6), wherein an exothermic peak derived from crystallization is observed at 0 to 150 ° C. in thermal analysis using an input compensation type differential calorimeter.
(8) The polyester foam according to any one of (1) to (7), wherein the temperature at which the peak time of isothermal crystallization of the polyester foam sheet is 1 to 60 seconds is in the range of 100 ° C to 150 ° C. Sheet.
(9) A light reflecting plate comprising the polyester foam sheet according to any one of (1) to (8).
(10) The light reflector according to (9), wherein an exothermic peak derived from crystallization observed at 0 to 150 ° C. in a thermal analysis by an input compensation type differential calorimeter is 0 to 3 J / g.
(11) To a melt containing 50 to 100% by weight of polytrimethylene terephthalate, 0.01 to 3% by weight of a substance in a gaseous state at normal pressure is injected and mixed and dissolved at the melting temperature of the melt. Then, after obtaining the melt, the melt is extruded from a die at an extrusion pressure of 5 to 100 MPa and molded, and the injected substance is foamed and cooled and solidified.
(12) The method for producing a polyester foam sheet according to (11), wherein the substance to be injected is in a gaseous state at normal temperature and normal pressure.
(13) After extruding the melt from a slit-shaped die, the melt is cast on a metal roll or belt, and then the melt is placed in water to be cooled and solidified (11) or (12) The manufacturing method of the polyester foam sheet of description.
(14) After injecting 0.01 to 3% by weight of a substance in a gaseous state at normal temperature and pressure into an amorphous sheet composed of a resin composition containing 50 to 100% by weight of polytrimethylene terephthalate, A method for producing a polyester foam sheet in which a crystal sheet is heated to 60 to 200 ° C. to foam the injected substance.
(15) The method for producing a polyester foam sheet according to any one of (11) to (14), wherein the substance to be injected is nitrogen.

  The polyester foam sheet according to the present invention has excellent light reflectivity, flexibility, heat insulation, and lightness. For this reason, when used for a light reflector, it has excellent light reflectivity, diffuse reflectivity, and has punching and bending workability that can be easily processed without wrinkles into a shape suitable for a light source. It is useful as a light reflector for a light box of a liquid crystal display device or a lighting fixture such as a fluorescent lamp. Moreover, the foamed sheet of the present invention is useful for various applications such as food containers, packaging materials, and building materials.

Schematic which shows one of the embodiment of the light reflecting plate which concerns on this invention.

The present invention will be specifically described below.
The polyester foamed sheet of the present invention is a foamed sheet comprising 50% to 100% by weight of polytrimethylene terephthalate (PTT) resin.

  Here, polytrimethylene terephthalate (PTT) is a polyester composed of PTT repeating units having terephthalic acid as an acid component and trimethylene glycol (also referred to as 1,3-propanediol, hereinafter abbreviated as “TMG”) as a diol component. It shows that.

  The polyester foam sheet of the present invention can achieve a sheet having excellent flexibility and moldability by comprising 50 wt% to 100 wt% of a PTT resin. This is because, firstly, an appropriate crystallization rate inherent to PTT, secondly, chemical stability derived from the molecular structure of PTT, which is a kind of saturated polyester with low chemical reactivity, and thirdly, zigzag. This is considered to be derived from the flexibility of the crystal that comes from the molecular skeleton structure.

  The proportion of the PTT resin is preferably 70% by weight to 100% by weight, more preferably 80% by weight to 100% by weight, from the viewpoints of sheet flexibility, ease of manufacture, and heat resistance, and 90% More preferably, it is from 100% by weight. The PTT may contain other copolymer components.

  Examples of the copolymer component include ethylene glycol, 1,1-propanediol, 1,2-propanediol, 2,2-propanediol 1,2-butanediol, 1,3-butanediol, and 1,4-butanediol. , Neopentyl glycol, 1,5-pentamethylene glycol, hexamethylene glycol, heptamethylene glycol, octamethylene glycol, decamethylene glycol, dodecamethylene glycol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4 -Cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 5-sodium sulfoisophthalic acid, 3,5-dicarboxylic acid benzenesulfonic acid tetramethyl Ester-forming monomers such as phosphonium salts, isophthalic acid, oxalic acid, succinic acid, adipic acid, dodecanedioic acid, fumaric acid, maleic acid, 1,4-cyclohexanedicarboxylic acid, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like These copolymers are exemplified.

  In order to increase the thermal stability and the flexibility of the sheet, the light reflectivity, and the heat resistance when the sheet is produced, it is preferable that the content of the above random copolymer is 30 mol% or less, and 20 mol. % Or less, more preferably 10 mol% or less.

  The degree of polymerization of the PTT of the present invention is preferably such that the intrinsic viscosity [η] is in the range of 0.5 dl / g to 4 dl / g. When the intrinsic viscosity is 0.5 dl / g or more, it becomes easy to produce a sheet, and it becomes easy to make the bubble size fine, and a foam sheet and a molded body having excellent strength and flexibility are obtained. It becomes easy. When the intrinsic viscosity [η] is 4.0 dl / g or less, it becomes easy to form a sheet. The intrinsic viscosity [η] is more preferably in the range of 0.7 dl / g to 3 dl / g, further preferably in the range of 0.9 dl / g to 2.5 dl / g, and in the range of 1.0 dl / g to 2 dl / g. Particularly preferred.

  The PTT of the present invention preferably has a carboxyl end group concentration of 0 eq / ton to 80 eq / ton. By doing in this way, it becomes easy to improve the weather resistance of a sheet | seat and a molded object, chemical resistance, hydrolysis resistance, and heat resistance. The carboxyl end group concentration is more preferably 0 eq / ton to 50 eq / ton or less, further preferably 0 eq / ton to 30 eq / ton or less, particularly preferably 0 meq / kg to 20 meq / kg, and the lower the better.

For the same reason, bis (3-hydroxypropyl) ether component (structure formula: —OCH ₂ CH ₂ CH ₂ OCH ₂ CH), which is a glycol dimer component in which TMG, which is a glycol component of PTT, is bonded via an ether bond. ₂ CH ₂ O— (hereinafter abbreviated as “BPE”) is preferably 0 wt% to 2 wt%. The content is more preferably 0.1% by weight to 1.5% by weight, and still more preferably 0.15% by weight to 1.2% by weight.

The polyester foam sheet of the present invention may contain various organic substances, inorganic substances, various additives and the like in addition to PTT. Even in such a case, the ratio of PTT needs to be in the above-described range. The proportion of PTT can be determined by analysis using ¹ H nuclear magnetic resonance spectrum (hereinafter abbreviated as “NMR”) using HFIP: CDCl ₃ = 1: 1 as a solvent. At this time, various PTT oligomers such as cyclic dimers and BPE are included in the PTT ratio.

  Examples of organic substances other than PTT include cyclic and linear PTT oligomers, monomers of acid components and glycol components constituting PTT, low molecular weight reactants derived therefrom, resins other than PTT, and various additives. . Resins other than PTT include thermoplastic polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate, polypropylene naphthalate, thermosetting polyester, nylon 6, nylon 66, nylon 11, nylon 12, etc. These include thermoplastic polyamides, polyolefins such as polyethylene and polypropylene, polycarbonates, polyurethanes, fluorine resins, silicone resins, polyphenylene sulfites, epoxy resins, acrylic resins, celluloses, and copolymer resins thereof.

  Examples of inorganic substances other than PTT include glass fiber, carbon fiber, talc, mica, wollastonite, kaolin clay, calcium carbonate, titanium dioxide, silica dioxide, and other inorganic fillers, inorganic lubricants, polymerization catalyst residues, and the like.

  Additives include organic and inorganic dyes and pigments, matting agents, heat stabilizers, flame retardants, antistatic agents, antifoaming agents, color modifiers, antioxidants, UV absorbers, crystal nucleating agents, and whitening agents. Agents, impurity scavengers, thickeners, surface conditioners and the like.

  As the heat stabilizer, a pentavalent or / and trivalent phosphorus compound or a hindered phenol compound is preferable. The addition amount of the phosphorus compound is preferably 2 ppm to 500 ppm, more preferably 10 ppm to 200 ppm as a weight ratio of the phosphorus element in the powder. As specific compounds, trimethyl phosphite, phosphoric acid, phosphorous acid, and tris (2,4-di-tert-butylphenyl) phosphite (Irgafos 168 manufactured by Ciba Specialty Chemicals Co., Ltd.) are preferable. .

  Here, the hindered phenolic compound is a phenolic derivative having a substituent having a steric hindrance at a position adjacent to a phenolic hydroxyl group, and a compound having one or more ester bonds in the molecule. The addition amount of the hindered phenol compound is preferably 0.001% by weight to 1% by weight, more preferably 0.01% by weight to 0.2% by weight with respect to the powder.

  Specific compounds include pentaerythritol-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (Irganox 1010 manufactured by Ciba Specialty Chemicals Co., Ltd.), 1, 1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (Ciba Specialty) Chemicals Co., Ltd. Irganox 1076, etc.), N, N′-hexamethylenebis (3,5-tert-butyl-4-hydroxy-hydrocinnamamide), ethylenebis (oxyethylene) bis [3- (5- tert-butyl-4-hydroxy-m-tolyl) propionate] (Ciba Irganox 245 manufactured by Specialty Chemicals Co., Ltd.), N, N′hexane-1,6-diylbis [3- (3,5 di-tert-butyl-4-hydroxyphenylpropionamide) (Ciba Specialty Chemicals Co., Ltd. Irganox 1098 etc.) etc. are preferable. Of course, using these stabilizers in combination is one of the preferred methods.

  It is preferable that a low molecular weight volatile impurity scavenger is added to the foamed sheet of the present invention. The scavenger is preferably a polymer or oligomer of polyamide or polyesteramide, a low molecular weight compound having an amide group or an amine group, or the like. The addition amount is preferably 0.001% by weight to 1% by weight, more preferably 0.01% by weight to 0.2% by weight, as a weight ratio to the powder.

  Specific compounds include polyamides such as nylon 6.6, nylon 6, and nylon 4.6, polymers such as polyethyleneimine, and a reaction product of N-phenylbenzenamine and 2,4,4-trimethylpentene. (Irganox 5057 manufactured by Ciba Specialty Chemicals Co., Ltd.), N, N′hexane-1,6-diylbis [3- (3,5 di-tert-butyl-4-hydroxyphenylpropionamide) (Ciba -Irganox 1098 manufactured by Specialty Chemicals Co., Ltd.), 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol ( Ciba Specialty Chemicals Co., Ltd. Irganox565 etc.) etc. are preferable. Of course, a combination of these is also one of the preferred methods.

  These substances may exist as particles or may be present in a form compatible with polymer molecules. In the present invention, particles having an average particle diameter of 0.01 μm to 100 μm are 0.1% by weight with respect to PTT. It is preferably contained in 30% by weight. The presence of such particles makes it easy to have many fine bubbles. The average particle size of the particles is more preferably 0.1 μm to 50 μm, still more preferably 0.3 μm to 20 μm, and particularly preferably 0.5 μm to 10 μm.

  The content of the particles is desirably larger as the average particle size of the particles is larger, and may be smaller as the particle size is smaller. However, the content is more preferably approximately 0.5% by weight to 20% by weight, and more preferably 1% by weight to 15% by weight. %, More preferably 2% by weight to 10% by weight. The particles preferably have a flat plate shape or needle shape rather than a true sphere, and preferably have protrusions. Further, the particles are preferably made of a material having low compatibility with PTT and low adhesion.

  Specific examples include powders made of fluorine-based resins such as talc and polytetrafluoroethylene (hereinafter abbreviated as “PTFE”), fluorine mica, plate-like alumina, layered silicate, and the like. Of these, fluorine-based resin and fluorine mica are preferable because the size of the bubbles can be made fine, and the flexibility, heat insulating property, and light reflectivity of the sheet can be improved. PTFE is most preferable from the viewpoint of heat resistance during sheet production.

  The thickness of the polyester foam sheet of the present invention is preferably 1 μm to 10 mm. When the thickness is 1 μm or more, the sheet can be easily handled, and when the thickness is 10 mm or less, heat molding is facilitated. The thickness of the polyester foam sheet is more preferably 10 μm to 5 mm, still more preferably 50 μm to 3 mm, and particularly preferably 100 μm to 2 mm.

The polyester foam sheet of the present invention is required to have an apparent density of 0.05 g / cm ^{3 to} 1.25 g / cm ³ and an average cell size of 0.01 μm to 50 μm. Only when the density and the bubble size are in this range, a foamed sheet having excellent light reflectivity and flexibility, is less likely to be crushed, and maintains the light weight.

Here, the average size of bubbles is the equivalent circle diameter calculated by using image analysis software from a cross-sectional image obtained by observing a sheet cross-section using a scanning electron microscope (hereinafter abbreviated as “SEM (Scanning Electron Microscope)”). Asking. Preferably the apparent density of the polyester foamed sheet is ^{0.1g / cm 3 ~1g / cm 3} , more preferably ^{0.15g / cm 3 ~0.8g / cm 3} , 0.2g / cm 3 further preferably ~0.7g / cm ^3.

  The average cell size of the polyester foam sheet is preferably 0.01 μm to 30 μm, more preferably 0.01 μm to 20 μm, and still more preferably 0.01 μm to 10 μm. From the viewpoint of imparting excellent light reflectivity and flexibility, the average bubble size is preferably 1/5 or less of the sheet thickness, more preferably 1/10 or less, and 1/50 or less. Is more preferable and 1/100 or less is particularly preferable.

  It is necessary that the bubbles in the polyester foam sheet of the present invention are not flat. As an indicator of non-flatness, the ratio (S / T) of the average size (S) in the surface direction of the bubbles and the average size (T) in the thickness direction can be used. It is necessary that it is 05-10, More preferably, it is 0.1-10, More preferably, it is 0.5-5, More preferably, it is 0.7-3, Most preferably, it is 1-2. When S / T is in the above range, bubbles in the foamed sheet are not easily crushed, and further, the foamed sheet of the present invention is less likely to be creased or scratched in combination with the main component of polytrimethylene terephthalate. .

  The crystallinity of the polyester foam sheet of the present invention is preferably adjusted according to the use and purpose to be used. When used as a base sheet to form a molded body of a desired shape by thermoforming, it is desirable to be in an amorphous state, while on the other hand, it is in a crystalline state when used as a container requiring heat resistance or a light reflecting plate. Is desirable.

  The crystal state index is 0 ° C. at a set rate of temperature increase of 10 ° C./min after holding the sheet at 0 ° C. for 3 minutes with an input compensation differential calorimeter (hereinafter abbreviated as “DSC (Differential Scanning Calorimetry)”). The size of the exothermic peak observed when the temperature is raised to 260 ° C. can be used. The fact that an exothermic peak is observed indicates that there is room for crystallization, that is, the degree of crystallinity is low, that it is easy to heat mold, and that the exothermic peak is not observed or is small, there is room for crystallization. This indicates that the crystallinity is high.

  When the base sheet for heat forming is used, it is preferable that an exothermic peak is observed, the calorific value is preferably 10 J / g or more, more preferably 20 J / g or more, and heat resistance is required. Is preferably 5 J / g or less, more preferably 3 J / g or less, still more preferably 1 J / g or less, and most preferably not observed. The upper limit of the exothermic peak is usually 90 J / g or less.

  In order to impart heat resistance by heat crystallization after molding, the temperature when the peak time of isothermal crystallization of the polyester foam sheet is 1 second to 60 seconds must be in the range of 100 ° C to 150 ° C. Is preferred. This is an index indicating the crystallization speed of the resin constituting the sheet, and can be achieved when the resin containing the PTT of the present invention has a specific structure. By setting it as such a sheet | seat, it can heat-mold and can crystallize easily in a comparatively short time, and can provide heat resistance.

  Here, the peak time of isothermal crystallization is a composition obtained by rapidly cooling and solidifying a polyester foam sheet melted at 280 ° C. in liquid nitrogen, and using an input compensation differential calorimeter (DSC). ) For 3 minutes at 0 ° C. and then heated from 0 ° C. to X ° C. at a set rate of heating of 500 ° C./min and derived from crystallization observed when held at X ° C. The time at which the endotherm peaks is shown. The above temperature range is preferably 5 ° C or higher continuously, more preferably 10 ° C, further preferably 20 ° C or higher, and a peak time of 1 second to 60 ° C over a temperature range of 100 ° C to 150 ° C. Particularly preferred is seconds.

  That is, when the polyester foam sheet according to the present invention is subjected to thermal analysis using an input compensation differential calorimeter (DSC), an exothermic peak derived from crystallization is observed between 0 ° C. and 150 ° C.

  The polyester foam sheet of the present invention preferably has a heat shrinkage rate of −2% to 5% at 150 ° C. in both the machine direction (MD) and the transverse direction (TD) from the viewpoints of heat resistance and post-processability. The thermal contraction rate is an index indicating unfixed strain of polymer molecules constituting the sheet, and 0% indicates that there is no strain. By setting the strain within a range as described above, it is possible to suppress dimensional changes and sheet deformation when used in a high temperature environment or when the temperature changes. The longitudinal direction (MD) indicates the take-up direction at the time of manufacturing the sheet, and the lateral direction (TD) indicates the orthogonal direction. Such a small strain can be achieved by not excessively stretching or imparting tension in the sheet manufacturing process, and is a feature of the sheet of the present invention that can generate bubbles without stretching using PTT as a raw material. is there.

  The thermal shrinkage is more preferably -1% to 3%, still more preferably -0.5% to 2%, and particularly preferably -0.3% to 1%. It is preferable that the shrinkage rate is also in directions other than the vertical and horizontal directions. Since the polyester foam sheet of the present invention is not actively stretched, it is easy to achieve such a low heat shrinkage rate, and it is also easy to reduce the shrinkage rate other than the length and width.

  The polyester foam sheet of the present invention preferably has an average light reflectance of 80% or more at a wavelength of 400 nm to 700 nm. It becomes suitable as a light reflecting plate by setting it as such a reflectance. The average light reflectance is more preferably 85% or more, and still more preferably 90% or more. Here, the light reflectance is a relative value when the reflectance of the barium sulfate white plate is 100%. Such light reflectance can be achieved by using PTT, which absorbs less light in the above-described range, as a raw material and having many fine bubbles without using a pigment that absorbs such light.

  The sheet of the present invention is desired to have a good color tone. The color tone is preferably 80 or more, more preferably 85 or more, and particularly preferably 90 or more, as L *, which is an indicator of lightness, in a state where coloring is not performed using a pigment or a dye. There is no particular upper limit for L *, but it is usually 100 or less. Moreover, it is preferable that b * which is the parameter | index showing yellowness is -5-10, It is more preferable that it is -3-8, -2-5 is still more preferable.

Moreover, it is preferable that the value which remove | divided the tensile elasticity modulus by the density of the sheet | seat of this invention is 50-1500 Mpa * cm < ³ > / g. In addition, the average value of MD direction and TD direction is used for a tensile elasticity modulus here. By using a sheet having such a value, it becomes easy to handle while having excellent flexibility. The value obtained by dividing the tensile elastic modulus by the density is more preferably 100 to 1200 MPa · cm ³ / g, further preferably 200 to 1100 MPa · cm ³ / g, and 300 to 1000 MPa · cm ³ / g. It is particularly preferred.

  Next, the manufacturing method of the polyester foam sheet concerning this invention is demonstrated.

  The polyester foam sheet of the present invention specifies a specific substance that is in a gaseous state at normal pressure at a melting temperature of the melt, which is 50% to 100% by weight of polytrimethylene terephthalate (PTT). It can be obtained by a “special melt extrusion foaming method” in which a quantity is injected, mixed and dissolved, extruded from a die under specific conditions, molded, foamed, and immediately cooled and solidified.

  Before describing a specific manufacturing method, first, the above-mentioned “special melt extrusion foaming method” will be described.

  Substances that are in a gaseous state at normal pressure can be dissolved to a saturated concentration in the resin melt. The saturation concentration decreases with decreasing system pressure. For this reason, the substance dissolved at a high concentration at a high pressure is separated from the resin into bubbles when the pressure decreases and the saturation concentration becomes lower than the dissolved concentration. At this time, after passing through a supersaturated state for a short time, first, very small bubble nuclei that are the origin of the bubbles are generated, and then the bubble nuclei grow and bubbles corresponding to the supersaturated concentration are generated.

  In the “special melt extrusion foaming method”, in order to generate a large number of fine bubbles, it is important to generate a large number of bubble nuclei which are the origin of the bubbles and to prevent the bubble nuclei from growing as much as possible.

  In order to generate a large number of bubble nuclei, the supersaturation concentration must be above a certain level. For this purpose, the gas substance is dissolved and dissolved in a high-pressure state at a predetermined pressure or higher so that the gas substance has a predetermined concentration or higher. It is necessary to release the pressure in a short time so that the substance does not become bubbles, and to reduce the saturation concentration rapidly.

  In order to prevent bubble nuclei from growing as much as possible, it is also important not to make the concentration of the substance that becomes a gas too high. This is because bubbles grow rapidly when the supersaturated concentration is too high. In addition, the melt whose pressure has been reduced to normal pressure needs to be quickly cooled and solidified to suppress bubble growth as much as possible.

  Further, according to the study by the present inventors, the use of a melt mainly composed of PTT makes it easier to make bubbles smaller than conventionally known with PET and PBT. The reason for this is not clear, but it seems to be derived from the zigzag molecular structure of PTT, an appropriate polar group concentration, and a relatively low melting temperature.

  In addition, in order to set the bubbles to a predetermined range of S / T, that is, a non-flat bubble, which is another object of the present invention, it is important that the sheet is not stretched or compressed. is there. In general, a fine foamed sheet of PET used as a light reflecting sheet generates bubbles with a foreign substance contained therein as a nucleus by stretching a solidified sheet, so that only flat bubbles can be obtained. Since the “special melt extrusion foaming method” of the present invention does not require such a stretching step, it is possible to obtain non-flat bubbles. However, also in the present invention, it is necessary to be careful not to stretch the sheet between the generation of bubbles by extrusion and the winding.

  The production method of the present invention will be specifically described below.

  The PTT composition can be obtained by a known method. For example, the PTT composition is prepared by using dimethyl terephthalate and trimethylene glycol, and if necessary, other copolymerization components as raw materials, and using titanium tetrabutoxide as a catalyst at ordinary pressure and a temperature of 180 ° C. to 260 ° C. After the exchange reaction, it can be obtained by performing a polycondensation reaction at 220 ° C. to 270 ° C. under reduced pressure.

  Additives necessary for producing a polyester foam sheet can be added by a method of adding at the time of polymerization, a method of adding by melt-kneading after the polymerization, or a method of combining them. It can be appropriately selected depending on the amount, the required performance, and the like. When various additives are added by melt-kneading, the PTT composition obtained by polymerization is cooled and solidified, or it is put together with various additives into a uniaxial or biaxial extruder in a molten state. Can be done.

  In the above-mentioned special melt extrusion foaming method, the melt comprising PTT is supplied to the supply unit using the extruder, melted by rotation of the screw, and melted out from the extruder. Is extruded from a slit-like die through a heated channel.

  As the extruder, a single-screw or twin-screw extruder, a tandem extruder in which two or more of these are connected in series, and the like can be used. As the screw of the extruder, it is preferable to use an optimum screw according to the properties of the PTT composition to be applied and the properties of the substance gas to be injected. It is desirable to set the extruder to a temperature at which no unmelted material remains and the thermal decomposition of the composition can be suppressed. The melting point of the PTT composition is preferably about + 0 ° C. to 30 ° C., and the melting point + 0 ° C. to 20 ° C. More preferably, the melting point is + 0 ° C to 15 ° C.

  If necessary, install a filter between the extruder and the base to remove foreign substances, install a gear pump to increase the quantitative supply, and improve the dispersibility of the injected substance Install a static mixer or install a heat exchange unit to keep the temperature constant. In such a case, it is desirable to appropriately select the pressure and temperature so that the substance injected in the vicinity of the equipment does not become large bubbles. Even when these devices are installed, it is desirable to set the temperature so that no unmelted material remains and the thermal decomposition of the composition can be suppressed, and it is preferable to set the melting point of the PTT composition + 0 ° C. to 30 ° C. .

  In the special melt extrusion foaming method, a substance in a gaseous state is injected into a melt at a normal pressure at a melting temperature. The material to be injected is preferably in a gaseous state even at normal temperature and normal pressure in view of ease of handling. Specific examples include inert compound blowing agents such as nitrogen, carbon dioxide, helium, argon, water, ethane, propane, butane, ethylene, propylene, petroleum ether, pentanes, hexanes, heptanes, toluene, trichloromethane, Aliphatic hydrocarbon blowing agents such as tetrachloromethane, trichlorofluoromethane, methanol, 2-propanol, isopropyl ether, methyl ethyl ketone, methyl chloride, dichloroethane, chloroform, fluoromethane, difluoromethane, trifluoroethane, chlorotrifluoromethane, dichloro Difluoromethane, fluorochloroethane, dichlorotetrafluoroethane and the like can be mentioned.

  Specific examples of fluorocarbons include CFC series CFCs (Freon) such as CFC-11 (R-11, R-12), CFC substitute (R-134a), CFC-11, CFC-12, CFC-113, and CFC-114. ) Halogenated hydrocarbon-based blowing agents and the like. Of these, nitrogen, helium, argon, and water are preferable, and nitrogen is particularly preferable from the viewpoint of not proceeding with crystallization of the sheet and reducing the bubble size.

  The amount of such a substance to be injected needs to be 0.01% by weight to 3% by weight from the viewpoint of making the bubbles finer and improving the surface state of the sheet. The injection amount is more preferably 0.02% by weight to 1% by weight, still more preferably 0.05% by weight to 0.5% by weight.

  Any method may be used as long as it is between the extruder and the die, but it is preferable to inject with the extruder because the substance can be uniformly injected into the melt.

  The melt is then extruded from the die and formed into a sheet-like shape, and the injected substance becomes bubbles by releasing the pressure. The die can be appropriately selected depending on the shape of the target sheet, but in order to obtain a sheet having a uniform thickness, a linear slit called T-die or I-die or a circular shape called round die is used. It is desirable to use a slit. It is desirable that the structure of the base is appropriately designed so that foaming does not occur in the base. For this purpose, the pressure of the melt at the inlet of the die needs to be 5 MPa or more, preferably 10 MPa or more, more preferably 12 MPa, and still more preferably 15 MPa or more. . Although there is no particular upper limit, the extrusion pressure is preferably 100 MPa or less, more preferably 50 MPa or less, considering the equipment structure.

  The die temperature at the time of extrusion is preferably set as low as possible so that the melt does not solidify. Specifically, the melting point of the composition is preferably + 0 ° C. to 30 ° C., and the melting point + 0 ° C. to 20 ° C. More preferably, the melting point is set to + 0 ° C. to 15 ° C., and it is preferable to set the melting point as low as possible within a range where the melt can be uniformly extruded.

  In the special melt extrusion foaming method, the melt formed and foamed into a sheet shape is then cooled and solidified. However, in the present invention, it is necessary to quickly cool and solidify so as to suppress the enlargement of bubbles. As a result, the bubble diameter of the foam sheet of the present invention can be reduced. Here, promptly refers to cooling so as to have the thermal characteristics of the above-described sheet, and specifically, the time for cooling the sheet below the crystallization temperature after being extruded from the die is within 60 seconds. Preferably, it is within 40 seconds, more preferably within 20 seconds. When obtaining an amorphous sheet, it is particularly important to cool and solidify immediately.

  As a method for achieving such cooling and solidification, a method in which the melt is brought into contact with a solid such as a cooling roll or a cooling belt controlled to a temperature lower than the crystallization temperature of the PTT composition, or a method in which the sheet is brought into contact with a liquid such as water. And a combination of these. Of these, a method in which a melt extruded from a slit-shaped die is cast (arranged) on a roll or a belt, and then put into water and immediately cooled and solidified is most preferable.

  Solids such as cooling rolls and belts are preferably made of metal having good heat conduction. The temperature of the solid or liquid to be contacted is more preferably 0 ° C. to 50 ° C., further preferably 0 ° C. to 30 ° C., and particularly preferably 0 ° C. to 20 ° C. The time from the extrusion from the die to the contact with the solid or liquid is preferably 0.05 to 10 seconds, more preferably 0.1 to 5 seconds, and 0.2 to 2 seconds. It is particularly preferable to do this.

  In the present invention, it is necessary to be careful not to stretch the sheet until the sheet in which bubbles are generated by extrusion is wound up. For this purpose, the winding speed is preferably 10 times or less, more preferably 8 times or less, and even more preferably 5 times or less the linear speed of the melt exiting the die. On the other hand, the lower limit is the speed ratio at which the sheet becomes flat. Specifically, it is preferably 0.9 times or more, more preferably 0.95 or more, and further preferably 1.0 times or more. By setting such a speed ratio, it becomes easy to set S / T within a predetermined range.

  The polyester foamed sheet of the present invention is quickly injected after injecting a specific amount of a substance in a gaseous state at normal temperature and pressure into an amorphous sheet comprising 50% by weight to 100% by weight of a polytrimethylene terephthalate resin composition. It can also be produced by a “special solid foaming method” in which the sheet is heated to a specific temperature to foam the injected substance. In this case, however, only a crystallized sheet is obtained.

  Before describing a specific manufacturing method, first, the above-mentioned “special solid foaming method” will be described.

  A substance in a gaseous state at normal pressure can be dissolved in the amorphous sheet to a concentration corresponding to the gas pressure. The dissolved concentration decreases with decreasing system pressure. In the “special melt foaming method”, when the saturation concentration is lower than the dissolved concentration, the resin separates from the resin to form bubbles, but the solid gradually releases from the surface and does not form bubbles. However, when the sheet is set to a temperature higher than the glass transition point, bubbles are formed as in the melt.

  In order to generate a large number of fine bubbles in the “special solid foaming method”, it is important to generate a large number of bubble nuclei that are the origin of the bubbles and to prevent the bubble nuclei from growing as much as possible.

  In order to generate a large number of bubble nuclei, inject a large amount of gas bubbles in a high pressure state above a predetermined pressure so that the gas material becomes a predetermined concentration or more, so that the injected material is not released from the surface, It is necessary to quickly bring the sheet to a temperature above the glass transition point.

  In order to prevent bubble nuclei from growing as much as possible, it is also important not to make the concentration of the substance that becomes a gas too high. This is because bubbles grow rapidly when the concentration is too high.

  Also, since PTT has a higher crystallization speed than PET, it is important to rapidly increase the sheet temperature. Since PBT has a very high crystallization rate, an amorphous sheet cannot be obtained, and a foamed sheet cannot be obtained by the same method.

  In addition, in order to set the bubbles to a predetermined range of S / T, that is, a non-flat bubble, which is another object of the present invention, it is important that the sheet is not stretched or compressed. is there. In the “special solid foaming method” of the present invention, it is possible to obtain bubbles that are not flat because no stretching or compression process is required. However, also in the present invention, care must be taken not to stretch the sheet after bubbles are generated by heating the sheet.

  The “special solid foaming method” of the present invention will be specifically described below.

  Specific examples of substances in a gaseous state at normal temperature and pressure injected into a sheet by a special solid foaming method include inert compound blowing agents such as nitrogen, helium and argon, ethane, propane, butane, ethylene, propylene, petroleum Ether, pentanes, hexanes, heptanes, toluene, trichloromethane, tetrachloromethane, trichlorofluoromethane, methyl chloride, dichloroethane, fluoromethane, difluoromethane, trifluoroethane, chlorotrifluoromethane, dichlorodifluoromethane, fluorochloroethane And dichlorotetrafluoroethane. Of these, nitrogen, helium, and argon are preferable from the viewpoint of reducing the bubble size, and nitrogen is particularly preferable.

  The amount of such a substance to be injected needs to be 0.01% by weight to 3% by weight from the viewpoint of making the bubbles fine. The injection amount is more preferably 0.02% by weight to 1% by weight, still more preferably 0.05% by weight to 0.5% by weight.

  The injection method can be achieved by placing an amorphous sheet in the gas atmosphere having a pressure of 0.5 MPa or more for 10 minutes or more. The pressure is more preferably 10 MPa or more, and further preferably 15 MPa or more. The time is more preferably 30 minutes or longer, still more preferably 60 minutes or longer, and particularly preferably 120 minutes or longer. When injecting the gas, the sheet temperature should be 40 ° C. or lower, preferably 20 ° C. or lower, more preferably 10 ° C. or lower so as not to crystallize.

  The sheet into which such gas is injected immediately heats to 60 ° C. to 200 ° C. to foam the injected material. Here, promptly means that the injected gas does not fall below the above amount. The heating temperature is more preferably 100 ° C to 200 ° C, further preferably 120 ° C to 200 ° C. At this time, in order to foam, it is important to heat rapidly so as to foam before crystallization. Such heating can be achieved by immersing in a heated inert liquid or contacting with a heated roll.

  Among the polyester foam sheets of the present invention, an amorphous one can be formed into a foam-molded product by molding.

  The foamed molded body is preferably crystallized during molding. By doing in this way, heat resistance can be improved. As the degree of crystallization, it is preferable that no exothermic peak derived from crystallization is observed between 0 ° C. and 150 ° C. when a polyester foam sheet is subjected to thermal analysis with an input compensation differential calorimeter (DSC). .

It is preferable that the apparent density of the polyester foamed sheet is ^{0.05g / cm 3 ~1.25g / cm 3} , more preferably from ^{0.1g / cm 3 ~1g / cm 3} , 0.15g / more preferably from cm ³ ~0.8g / cm ^3, particularly preferably ^{0.2g / cm 3 ~0.7g / cm 3} .

  The shape of the molded body can be appropriately selected according to the application. For example, box shape, cup shape, corrugated plate shape, etc. are mentioned. Examples of a method for forming such a molded body include press molding, straight molding, drape molding, plug assist molding, vacuum molding, vacuum / pressure forming, and pressure forming, among which vacuum / pressure forming is more preferable.

  When molding, it is preferable to first heat the sheet to a temperature of 30 ° C. to 80 ° C. by means of heater radiation or a heating plate. By doing so, it becomes easy to soften the sheet without crystallizing, and the moldability and transferability are improved. The temperature is more preferably 40 ° C to 70 ° C, further preferably 45 ° C to 65 ° C, and particularly preferably 50 ° C to 60 ° C.

  Next, the sheet is formed by bringing it into contact with a mold, and the mold temperature at this time is preferably 60 ° C. to 180 ° C. In the present invention, the polyester foam sheet is almost in an amorphous state at the time of shaping in order to ensure moldability, but after shaping, it is important to crystallize the molded body in order to ensure heat resistance. is there. For this purpose, it is preferable to crystallize the molded body by controlling the mold temperature within a certain temperature range. The mold temperature is preferably 65 ° C. or higher in order to give sufficient heat resistance to the molded body, and it is preferably 180 ° C. or lower in order to suppress release from the mold or collapse of bubbles after molding. The mold temperature is more preferably 80 ° C to 160 ° C, and particularly preferably 100 ° C to 150 ° C. It is also a preferable method to raise the temperature of the mold after molding or to heat the sheet to the temperature within the above range by heating from the outside.

In the present invention, the thermoforming can be performed by stacking two or more polyester foam sheets. In this case, it is preferable to provide an air vent hole in the sheet on the side where the pressure is increased during molding so that the air between the sheets is easy to escape.
The polyester foam sheet of the present invention is extremely suitable as a light reflecting plate for lighting equipment such as a light box of a liquid crystal display device and a fluorescent lamp.

The functions required of these light reflecting plates include, firstly, having high reflectivity, particularly high diffuse reflectivity. The polyester foam sheet of the present invention contains a large number of fine bubbles such that the average cell size is 0.01 μm to 50 μm in the inside so that the apparent density is 0.05 g / cm ^{3 to} 1.25 g / cm ^3. High reflectivity, particularly high diffuse reflectivity is achieved by not being colored, that is, by low light absorption.

  Secondly, it can be processed into a shape corresponding to the light source and can retain this shape. It is desirable that the processing can be easily performed (processing can be performed with a small force) and that the processing range is wide, that is, it can be processed into various shapes.

  The light reflecting plate of the present invention has desirable flexibility. In order to express only flexibility, it is possible to reduce the thickness of the sheet, but if this is done, the rigidity will be lost too much, the force to hold the shape will be weakened, and it will deform due to environmental changes and slight external force Sometimes. If it is deformed, light cannot be reflected in a desired direction, and in the case of a liquid crystal display panel, light and darkness occurs on the screen. The light reflecting plate of the present invention is composed of polytrimethylene terephthalate having crystal flexibility that is composed of a zigzag molecular skeleton structure, and further contains many fine bubbles as described above. It has a honeycomb structure composed of thin partition walls of ultrafine cells and is flexible without reducing the thickness. As a result, it is possible to achieve both flexibility, that is, workability and rigidity.

  Further, the light reflector of the present invention is made of polytrimethylene terephthalate having a crystal elastic recovery of 50% by weight to 100% by weight having a zigzag molecular skeleton structure, and S / T is 0.05 to 10%. The average cell size is 0.01 μm to 50 μm, and it is not flat and contains a large number of fine cells, so it becomes a honeycomb structure that is not easily crushed, so it has high elastic recovery, and it may be bent or wrinkled. It is easy to process into a shape such as a curved surface without doing so. Furthermore, there is a high possibility that even if the processing is somewhat failed, it can be restored to the original shape and processed again.

  Such characteristics cannot be expected from a light reflecting plate made of a normal PTT sheet or PET fine foam sheet.

  There are linear light sources such as fluorescent lamps, large dot-shaped objects such as incandescent lamps, and small dot-like objects such as LEDs, or a single light source or a combination of many light sources. Therefore, it is very preferable that various shapes can be easily formed as described above. If it is bent or wrinkled, it will not be possible to reflect light in the desired direction, and the reflectance of the wrinkled part will be lowered, and in the case of a liquid crystal display panel, streaky light and dark may be produced. Resulting in.

  The light reflection plate of the present invention preferably has an average light reflectance at a wavelength of 400 nm to 700 nm of 80% or more, more preferably 85% or more, and particularly preferably 90% or more.

  The thickness is preferably from 100 μm to 2 mm, more preferably from 200 μm to 1.5 mm, and particularly preferably from 500 μm to 1.2 mm in view of handling properties, rigidity at installation, and light concealment.

  The light reflection plate desirably has heat resistance because the light source generates heat. For this purpose, a crystalline plate is preferable. As an index of crystallinity, whether or not an exothermic peak derived from crystallization is observed between 0 ° C. and 150 ° C. when thermal analysis is performed with an input compensation differential calorimeter, the exothermic peak area Is preferably 5 J / g or less, more preferably 3 J / g or less, still more preferably 1 J / g or less, and of course most preferably not observed at all.

  The shape of the light reflecting plate is selected according to the light source, and examples thereof include a flat plate shape, a corrugated plate shape, and a box shape. Further, a conical shape, a pyramid shape, and a bowl shape that can cover light and reflect light in one direction are also preferable shapes.

  Processing into such a shape can be performed by slitting, cutting, punching with a mold, bending processing, press processing, thermoforming, etc. Of these, when heat resistance is required or the shape of When self-holding properties are required, it is desirable to perform thermoforming. This is because the deformed portion is heat-set by thermoforming, so that the dimensional accuracy is excellent.

  Hereinafter, although an embodiment of the invention is described in detail based on an example, the present invention is not limited to these examples. The main measurement values in the present invention were measured by the following method.

(1) Polytrimethylene terephthalate (PTT) content, BPE content:
The PTT content (% by weight) is obtained by 1H-NMR measurement using a solution obtained by dissolving 100 mg of a sheet in HFIP: CDCl ₃ = 1: 1 and filtering insoluble components with MEMBRANE FILTER (1 μm, PTFE). It was. As a measuring machine, FT-NMR DPX-400 (manufactured by Bruker) was used. Moreover, the insoluble component removed by filtration was used for measuring the weight after vacuum drying and determining the PTT content.

(2) Intrinsic viscosity [η]:
Intrinsic viscosity [η] was extrapolated to a zero concentration by using a Ostwald viscometer, and the ratio ηsp / C of specific viscosity ηsp and concentration C (g / 100 milliliters) in o-chlorophenol at 35 ° C. It calculated | required according to 1 type | formula.

[Equation 1]
[Η] = lim (ηsp / C)
C → 0

(3) Carboxyl end group concentration:
1 g of PTT composition was dissolved in 25 ml of benzyl alcohol, and then 25 ml of chloroform was added, followed by titration with a 1/50 N potassium hydroxide benzyl alcohol solution. When there was no titration value VA (ml) and PTT composition It calculated | required according to the following Numerical formula 2 from the blank value V0.

[Equation 2]
Carboxyl end group concentration (eq / ton) = (VA−V0) × 20

(4) Apparent density:
The polyester foam sheet was dried at 50 ° C., and the weight when reaching a constant weight value was divided by the volume. The volume was determined by immersing the sheet in water.

(5) Exothermic peak derived from crystallization:
The presence or absence of an exothermic peak derived from crystallization and the exothermic peak area were measured at 0 ° C. using a sheet or molded body, Pyris 1 (with a cooling unit) manufactured by Perkin Elmer as an input compensated differential calorimeter (DSC). After maintaining for a minute, the temperature was raised from 0 ° C. to 260 ° C. at a set rate of temperature increase of 10 ° C./min, and a thermal analysis was performed for observation.

(6) Peak time of isothermal crystallization:
The peak time of isothermal crystallization was obtained by Perkin Elmer Co. as an input compensated differential calorimeter (DSC) using a composition obtained by rapidly cooling and solidifying a melted sheet at 280 ° C. in liquid nitrogen. Using Pyris 1 (with cooling unit), hold at 0 ° C for 3 minutes, then heat from 0 ° C to X ° C at a set temperature increase rate of 500 ° C / min, hold at X ° C, and crystallize It was determined by measuring the time when the endothermic amount derived from the peak of the heat absorption.

(7) Ratio S / T of the average diameter of bubbles, the average size in the surface direction (S), and the average size in the thickness direction (T):
The ratio S / T between the average bubble diameter, the average size in the plane direction (S), and the average size in the thickness direction (T) is the sheet in both the MD direction (sheet longitudinal direction) and the TD direction (sheet width direction). The cross section was determined using image analysis software from the cross-sectional image observed using a scanning electron microscope (hereinafter abbreviated as “SEM”). As an image analysis software, image-Pro Plus ver. 4.0 was used. The average diameter of the bubbles was obtained by averaging the average values of the major axis and the length projected on a single axis of an equivalent ellipse approximating the cross section of the bubble to an ellipse in each of the MD and TD directions. S and T are the rectangles circumscribed by the bubbles (the average of the height and width of the smallest rectangle that completely surrounds the bubbles and has a side parallel to the sheet surface direction, and the MD and TD directions. The average was obtained for each direction.

(8) Thermal contraction rate:
In accordance with JIS K7133, the dimensional change when the film was heat-treated at 150 ° C. for 30 minutes without applying tension was measured to obtain the thermal shrinkage rate.

(9) Average light reflectance:
The average light reflectivity was obtained by calculating the simple average value of the total reflectivity with a wavelength of 400 nm to 700 nm measured every 10 nm using a UV-2200 manufactured by Shimadzu Corporation with the incident angle shifted by 8 °. At this time, the measuring apparatus was adjusted with barium sulfate powder as 100%.
(10) Color tone (L value, b * value):
Measurement was performed using a color computer of Suga Test Instruments Co., Ltd.

(11) Flexibility-1:
The state when the sheet was bent to 180 ° C. was observed. The broken piece was evaluated as “×”, the case where a crack was generated on the surface was evaluated as “Δ”, and the case where no break or crack was generated was evaluated as “◯”.
(12) Flexibility-2:
A tensile modulus was obtained by a tensile test according to ASTM D882, and a value obtained by dividing the modulus by density was used as an index of flexibility and ease of processing.
(13) Workability:
The processing state when bending with a curvature of 3 mmφ was observed. A sample which was bent without causing a desired curvature or wrinkled on the surface was evaluated as “X”, and a sample which was not bent and wrinkled was evaluated as “◯”.

[Example 1]
An intrinsic viscosity [η] of 1.3 dl / g, a carboxyl end group concentration of 10 eq / ton, a BPE content of 0.5% by weight of PTT of 98.8 parts by weight, PTFE having an average particle diameter of 5 μm, 1 part by weight, heat stability 0.1 parts by weight of Irgafos 168 manufactured by Ciba Specialty Chemicals Co., Ltd. as an agent, and 0.1 part by weight of Irganox 1098 manufactured by Ciba Specialty Chemicals Co., Ltd. as a scavenger for low molecular weight volatile impurities The melted PTT composition having a melting point of 225 ° C. was fed to a single screw extruder of 50 mmφ set at 235 ° C. and then melted, and then passed through a flow path heated to the same temperature as the extruder to have a width of 100 mm and an interval of 0.5 mm. A T-die was extruded at a linear speed of 5 m / min to form a sheet.

  At this time, 0.1% by weight of nitrogen with respect to the composition was injected from the middle of the extruder to be mixed and dissolved with the melt. Moreover, the pressure of the melt at the T-die entrance was 15 MPa. The melt extruded from the T-die was cast on a metal rotating roll 50 mm away, and then introduced into cooling water to be cooled and solidified to obtain a foamed sheet. At this time, the rotating roll and the cooling water are controlled to be 10 ° C., the time from the extrusion of the melt to the contact with the rotating roll is 0.6 seconds, and the crystallization temperature of the composition is 68 ° C. or less. The cooling time was within 20 seconds.

The obtained polyester foam sheet had a thickness of 1 mm and a width of 100 mm, and the sheet was not cracked even when bent at 180 °. The intrinsic viscosity [η] is 1.15 dl / g, the carboxyl end group concentration is 15 eq / ton, the BPE content is 0.5% by weight, the density is 0.6 g / cm ³ , the average cell diameter is 20 μm, ( The film had fine and non-flat bubbles (S / T) of 1.3, an excellent light reflectivity of 85%, and a heat shrinkage of 0.2% in both MD / TD directions. Also, the heat of crystallization was 15 J / g, and the peak time of isothermal crystallization was considered to have good thermoformability between 1 second and 60 seconds over the entire range of 100 ° C to 150 ° C. .

The obtained polyester foam sheet was molded by a vacuum / pressure forming method to obtain a cup-shaped molded product having an inner diameter of 200 mm and a depth of 50 mm. For forming, first, the sheet was heated to 55 ° C. with heater radiation, and then brought into contact with an aluminum mold heated to 120 ° C. at a vacuum degree of 720 mmH and a pressurizing pressure of 0.2 MPa. This was carried out by holding for 2 seconds for crystallization. The obtained foamed molded article was a lightweight molded article with an apparent density of 0.6 g / cm ³ . The results are shown in Tables 1 and 2 below.
In the table, “ME” means a special melt extrusion foaming method, “S” means a special solid foaming method, and “COOH” means a carboxyl end group concentration. In addition, the values described in the item “thermal shrinkage” mean values in MD / values in TD, respectively.

[Examples 2 to 4]
A polyester foam sheet was obtained in the same manner as in Example 1 except that the conditions shown in Tables 1 and 2 below were changed. The results are shown in Tables 1 and 2 below. In any case, the polyester foam sheet had excellent lightness and flexibility within the scope of the present invention.

  In Example 2, by increasing the discharge pressure and adding a large amount of PTFE particles having a small particle size, a polyester foam sheet having finer bubbles and high light reflectance was obtained.

  Further, in Example 3, the amount of gas injection was increased, and in Example 4, the thickness of the sheet was changed, but an excellent polyester foam sheet was obtained as in Example 1.

[Example 5]
Similar to Example 1 except that PTT having an intrinsic viscosity [η] of 0.9 dl / g, a carboxyl end group concentration of 20 eq / ton, and a BPE content of 0.5 wt% was used and the thickness was 0.7 mm. Thus, a polyester foam sheet was obtained. At this time, the interval between the T dies was adjusted so that the pressure of the melt at the T die entrance was 20 MPa or more. The results are shown in Tables 1 and 2 below. The obtained polyester foam sheet was within the scope of the present invention, and had excellent lightness, flexibility, and light reflectance.

[Example 6]
A polyester foam sheet was obtained in the same manner as in Example 1 except that a composition containing 3 parts by weight of fluorine mica having an average particle size of 6 μm (Somasif MAE manufactured by Corp Chemical Co., Ltd.) was used instead of PTFE. At this time, the interval between the T dies was adjusted so that the pressure of the melt at the T die entrance was 15 MPa or more. The results are shown in Tables 1 and 2 below. The obtained polyester foam sheet was within the scope of the present invention, and had excellent lightness, flexibility, and light reflectance.

[Examples 7 and 8]
An intrinsic viscosity [η] of 1.15 dl / g, a carboxyl end group concentration of 15 eq / ton, a BPE content of 94.8 parts by weight of PTT with an average particle diameter of 2 μm, 5 parts by weight of PTFE, and heat stable 0.1 parts by weight of Irgafos 168 manufactured by Ciba Specialty Chemicals Co., Ltd. as an agent, and 0.1 part by weight of Irganox 1098 manufactured by Ciba Specialty Chemicals Co., Ltd. as a scavenger for low molecular weight volatile impurities A non-foamed sheet having a thickness of 0.4 mm made of a PTT composition having a melting point of 225 ° C. was placed in a nitrogen atmosphere of 20 MPa for 120 minutes in Example 7 while maintaining the temperature at 20 ° C. or lower. In Example 8, in a state where the temperature was kept at 20 ° C. or lower, argon was added in an argon atmosphere of 15 MPa for 100 minutes. After injecting amount%, to obtain a foamed rapidly heated by placing 180 ° C. oil bath within three minutes of extraction polyester foam sheet. The results are shown in Tables 1 and 2 below. The obtained polyester foam sheets were all within the scope of the present invention, and had excellent lightness, flexibility, and light reflectance.

[Comparative Examples 1 and 2]
In Comparative Example 1, instead of 95 parts by weight of PTT, 95% by weight of PET having an intrinsic viscosity [η] of 0.85 dl / g and a carboxyl end group concentration of 30 eq / ton and 5 parts by weight of talc having an average particle diameter of 5 μm were compared. Example 2 was the same as Example 1 except that 95 parts by weight of PBT having an intrinsic viscosity [η] of 1.0 dl / g and a carboxyl end group concentration of 50 eq / ton and 5 parts by weight of talc having an average particle diameter of 5 μm were used. Thus, a polyester foam sheet was obtained. In Comparative Example 2, the temperatures of the extruder, T-die, etc. were set 30 ° C. higher than in Example 1. The results are shown in Tables 1 and 2 below.

  The sheet of Comparative Example 1 had a large bubble diameter and low light reflectance. In addition, the sheet of Comparative Example 2 was inferior in flexibility, not only having a large bubble diameter and low light reflectance, but also breaking into two when bent at 180 °.

[Comparative Example 3]
A foamed sheet was obtained in the same manner as in Example 1 except that the discharge pressure was 2 MPa by adjusting the interval between the T dies. The results are shown in Tables 1 and 2 below. The obtained sheet had a large bubble diameter and low light reflectance.

[Comparative Example 4]
An attempt was made to obtain a foamed sheet in the same manner as in Example 7 except that 0.8 wt% carbon dioxide gas was injected under the condition that the temperature was kept at 20 ° C. or less using 4 MPa carbon dioxide gas instead of nitrogen. . However, no foaming was observed even when placed in an oil bath at 180 ° C. The results are shown in Tables 1 and 2 below.

[Comparative Example 5]
A roll of a non-oriented amorphous sheet having a thickness of 250 μm made of the same PET as used in Comparative Example 1 and a polyethylene non-woven fabric was wound for 48 hours in acetone vapor at atmospheric pressure and then taken out. It was impregnated with carbon dioxide gas of 5 MPa at 2 ° C. for 2 hours. Then, it put in the heating furnace set to 200 degreeC, and it was made to foam and the foamed sheet was obtained. The obtained foam sheet was a foam sheet having a thickness of 1 mm, an apparent density of 0.4 g / cm 3, an average cell diameter of 3 μm, an S / T of 1.2, and a light reflectance of 90%. When the sheet was evaluated for flexibility and workability in the same manner as the film of the present invention, it was not easy to bend, and many wrinkles were generated when the sheet was bent to a curvature of 3 mmφ.

[Example 9]
Using the sheets of Examples 1 and 2 and Comparative Examples 1 and 3, a 26-inch size liquid crystal display panel backlight unit was prepared. As the light source, 16 cold cathode tubes were used, and the foam sheets of Examples 1 and 2 and Comparative Example 3 were used as a wave-shaped light reflecting plate as shown in FIG. 1 by vacuum forming. In FIG. 1, the cold cathode tube was placed 5 mm above the center of the recess on the lower surface of the foam sheet. On the other hand, since the sheet of Comparative Example 2 was difficult to process, it was used as a flat light reflection plate, and the cold cathode tubes were arranged on the sheet 5 mm at the same intervals as described above. A 1.5 mm thick diffuser plate (Delaglass DS manufactured by Asahi Kasei Chemicals Corporation) was drawn on the light source to form a backlight unit.

  When the light reflecting plate made of the sheets of Examples 1 and 2 was used, the luminance was high, and luminance unevenness derived from the cold cathode tube was not recognized.

  On the other hand, when the light reflecting plate made of the sheets of Comparative Examples 1 and 2 is used, not only the luminance is lowered as compared with Examples 1 and 2, but also streaky luminance unevenness derived from the cold cathode tube is visually observed. It was recognized in. In particular, in the case of Comparative Example 2, the luminance unevenness was remarkable.

Further, when the backlight unit using the light reflection plate of Comparative Example 1 was kept on for 10 hours, the temperature rose locally to 80 ° C., but no deformation was observed in the light reflection plate.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

  This application is based on a Japanese patent application (Japanese Patent Application No. 2006-011194) filed on Jan. 19, 2006, the contents of which are incorporated herein by reference.

  The polyester foam sheet of the present invention has excellent flexibility, heat insulation, light weight, and light reflectivity. For this reason, as an example of utilization of this invention, it is useful for various uses, such as a food container, a packaging material, a building material, and a light reflection board. In the case of a light reflecting plate, it has excellent light reflectivity and diffuse reflectivity, and has punching and bending workability that can be easily processed without wrinkles into a shape suitable for a light source. It is useful as a light reflector for a light box of a display device or a lighting fixture such as a fluorescent lamp.

Claims (15)

A polyester foam sheet,
Containing 50 to 100% by weight of polytrimethylene terephthalate,
The apparent density is 0.05 to 1.25 g / cm ³ ,
Including bubbles having an average bubble size of 0.01 to 50 μm, and
The polyester foam sheet whose ratio (S / T) of the average size (S) of the surface direction of the said bubble and the average size (T) of the thickness direction is 0.05-10.   The polyester foam sheet according to claim 1, wherein the thickness of the polyester foam sheet is 1 μm to 10 mm.   The average bubble size of the bubbles is 0.01-30 μm, and the ratio (S / T) of the average size (S) in the surface direction of the bubbles to the average size (T) in the thickness direction is 0.7- The polyester foam sheet according to claim 1 or 2, wherein the polyester foam sheet is 3.   The polyester foam sheet according to any one of claims 1 to 3, wherein a heat shrinkage rate of the polyester foam sheet at 150 ° C is -2 to 5%.   The polyester foam sheet according to any one of claims 1 to 4, wherein an average light reflectance of the polyester foam sheet with respect to light having a wavelength of 400 to 700 nm is 80% or more.   The polyester foam sheet according to any one of claims 1 to 5, which is produced by a melt extrusion method.   The polyester foam sheet according to any one of claims 1 to 6, wherein an exothermic peak derived from crystallization is observed between 0 to 150 ° C in thermal analysis using an input compensation type differential calorimeter.   The polyester foam sheet according to any one of claims 1 to 7, wherein a temperature at which a peak time of isothermal crystallization of the polyester foam sheet is 1 to 60 seconds is in the range of 100C to 150C.   The light reflection board comprised from the said polyester foam sheet of any one of Claims 1-8.   The light reflecting plate according to claim 9, wherein an exothermic peak derived from crystallization observed between 0 to 150 ° C. in a thermal analysis by an input compensation type differential calorimeter is 0 to 3 J / g. A melt containing 50 to 100% by weight of polytrimethylene terephthalate is mixed and dissolved by injecting 0.01 to 3% by weight of a substance in a gaseous state at normal pressure at the melting temperature of the melt. After getting
A method for producing a polyester foam sheet, in which the melt is extruded and molded from a die at an extrusion pressure of 5 to 100 MPa, and the injected substance is foamed and cooled and solidified.   The method for producing a polyester foam sheet according to claim 11, wherein the substance to be injected is in a gaseous state at normal temperature and normal pressure.   13. The melt according to claim 11 or 12, wherein the melt is extruded from a slit-shaped die, and then the melt is cast on a metal roll or belt, and then the melt is placed in water to be cooled and solidified. A method for producing a polyester foam sheet.   After injecting 0.01 to 3% by weight of a substance in a gaseous state at normal temperature and pressure into an amorphous sheet composed of a resin composition containing 50 to 100% by weight of polytrimethylene terephthalate, A method for producing a polyester foam sheet, which is heated to 60 to 200 ° C. to foam the injected substance.   The method for producing a polyester foam sheet according to any one of claims 11 to 14, wherein the substance to be injected is nitrogen.

Images