U.S. patent application number 09/879100 was filed with the patent office on 2002-01-24 for polyester resin and molded article.
Invention is credited to Hayashi, Takeo, Hirokane, Takeshi, Kurokawa, Masahiro, Oguro, Dai, Yamamoto, Koji.
Application Number | 20020010309 09/879100 |
Document ID | / |
Family ID | 27343710 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020010309 |
Kind Code |
A1 |
Oguro, Dai ; et al. |
January 24, 2002 |
Polyester resin and molded article
Abstract
The polyester resin of the present invention is produced by
polymerizing a monomer mixture comprising a glycol component
containing 5 to 60 mol % of a spiroglycol represented by Formula I:
1 and 30 to 95 mol % of ethylene glycol, and a dicarboxylic acid
component containing 80 to 100 mol % of terephthalic acid and/or an
ester thereof. The polyester resin has (1) an intrinsic viscosity
of 0.4 to 1.5 dL/g, (2) a melt viscosity of 700 to 5,000
Pa.multidot.s, (3) a molecular weight distribution of 2.5 to 12.0;
and (4) a glass transition temperature of 90.degree. C. or higher
and a cooling crystallization exotherm peak of 5 J/g or lower. The
polyester resin of the present invention is excellent in heat
resistance, transparency, mechanical properties, moldability and
fabrication qualities and useful for producing shaped articles such
as films, sheets, hollow containers and foamed products.
Inventors: |
Oguro, Dai; (Kanagawa-ken,
JP) ; Yamamoto, Koji; (Kanagawa-ken, JP) ;
Hayashi, Takeo; (Kanagawa-ken, JP) ; Hirokane,
Takeshi; (Kanagawa-ken, JP) ; Kurokawa, Masahiro;
(Kanagawa-ken, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
27343710 |
Appl. No.: |
09/879100 |
Filed: |
June 13, 2001 |
Current U.S.
Class: |
528/272 ; 428/98;
528/300; 528/308.6; 528/403 |
Current CPC
Class: |
C08J 2367/02 20130101;
Y10T 428/1352 20150115; C08G 63/672 20130101; Y10T 428/1376
20150115; C08J 2201/03 20130101; Y10T 428/24 20150115; C08J 9/141
20130101 |
Class at
Publication: |
528/272 ;
528/300; 528/308.6; 528/403; 428/98 |
International
Class: |
B32B 005/00; C08G
063/66 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2000 |
JP |
177070/2000 |
Oct 23, 2000 |
JP |
322673/2000 |
Dec 5, 2000 |
JP |
370580/2000 |
Claims
What is claimed is:
1. A polyester resin produced by polymerizing a monomer mixture
comprising a glycol component containing 5 to 60 mol % of a
spiroglycol represented by Formula I: 4and 30 to 95 mol % of
ethylene glycol, and a dicarboxylic acid component containing 80 to
100 mol % of terephthalic acid and/or an ester thereof, the
polyester resin satisfying the following requirements (1) to (4):
(1) an intrinsic viscosity of 0.4 to 1.5 dL/g when measured at
25.degree. C. in a 6/4 by mass mixed solvent of phenol
/1,1,2,2-tetrachloroethane; (2) a melt viscosity of 700 to 5,000
Pa.multidot.s when measured at 240.degree. C. under a shear rate of
100 s.sup.-1; (3) a molecular weight distribution of 2.5 to 12.0;
and (4) a glass transition temperature of 90.degree. C. or higher,
and a cooling crystallization exotherm peak of 5 J/g or lower, when
measured by a differential scanning calorimeter.
2. The polyester resin according to claim 1, wherein the glycol
component contains 20 to 40 mol % of the spiroglycol represented by
Formula I and 50 to 80 mol % of ethylene glycol.
3. The polyester resin according to claim 1, wherein the
dicarboxylic acid component contains 95 to 100 mol % of
terephthalic acid and/or an ester thereof.
4. The polyester resin according to claim 1, wherein the glycol
component contains 15 to 60 mol % of the spiroglycol represented by
Formula I, and 40 to 85 mol % of ethylene glycol.
5. The polyester resin according to claim 1, which is made into a
polyester film or sheet, the polyester film or sheet having a
drop-weight breaking strength of 10 kJ/m or higher when vertically
applying an impact energy of 300 J by dropping a semispherical
weight of 20 mm diameter on the polyester film or sheet.
6. The polyester resin according to claim 1, which is made into a
hollow container.
7. A process for producing a foamed polyester sheet, comprising:
melt-kneading the polyester resin according to claim 4 in the
presence of a foaming agent in an extruder; and extruding the
polyester resin into a low pressure region.
8. A foamed polyester sheet produced by the process according to
claim 7.
9. The foamed polyester sheet according to claim 8, wherein the
sheet has a thickness of 0.2 to 7 mm and a closed cell content of
at least 50%.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polyester resin, and more
particularly to a polyester resin for films, sheets or hollow
containers having excellent heat resistance, transparency,
mechanical properties, moldability and fabrication qualities, and a
molded article produced from the polyester resin.
[0003] 2. Description of the Prior Art
[0004] As well known in the arts, PET (polyethylene terephthalate)
is an industrially valuable polyester because of its superiority in
mechanical properties such as tensile strength, elongation and
Young's modulus, physical properties such as heat resistance and
dimensional stability and chemical properties such as chemical
resistance and water resistance, and low costs. For example, PET
has been widely used in various applications such as fibers, tire
cords, bottles and films. However, when PET is formed into thick
sheets, i.e., plates, its high crystallization rate is likely to
cause whitening of the plates due to crystallization in the
fabrication step, thereby failing to provide transparent plates. To
avoid this disadvantage, PET modified with cyclohexane dimethanol,
etc. has been used. Also, in the production of PET bottles,
expensive germanium oxide has been used as a catalyst to reduce the
crystallization rate, or PET modified by copolymerizing a modifying
component such as isophthalic acid and cyclohexane dimethanol has
been used.
[0005] However, the modified PET is less heat-resistant, and
therefore, its use in the application requiring a high heat
resistance, for example, illumination plates, carports and
heat-resistant food containers, is limited.
[0006] U.S. Pat. No. 2,945,008 discloses, in Examples 9 and 10,
that a diol component (glycol component) comprising ethylene glycol
and
3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane
(hereinafter occasionally referred to merely as "SPG") represented
by Formula I: 2
[0007] is polymerized with a dicarboxylic acid component comprising
dimethyl terephthalate in the presence of a titanium compound
catalyst to produce a polyester which melts at 180 to 220.degree.
C. The modified PET disclosed therein is expected to show a high
heat resistance as compared with non-modified PET because the
modified PET contains SPG component having a rigid structure.
However, the U.S. Patent does not specify properties of the
modified PET such as intrinsic viscosity, molecular weight
distribution, melt viscosity, mechanical characteristics and heat
resistance. In addition, the modified PET fails to stably show
effective moldability and heat resistance or suffers from drastic
deterioration in impact resistance, depending upon its chemical
composition and properties. Therefore, the modified PET is not
necessarily a practically usable molding material.
[0008] Japanese Patent Application Laid-Open No. 3-130425 and
Japanese Patent Publication Nos. 5-69151 and 6-29396 have proposed
to use a polyester produced from a glycol component containing SPG
as high shrinkage filament of combined filament yarn composed of
different shrinkage filaments, coating agent and adhesive. However,
in these prior arts, there is no description concerning molecular
weight distribution, melt viscosity and mechanical properties of
the modified PET. Since the modified PET fails to stably show an
effective heat resistance or suffers from drastic deterioration in
impact resistance depending upon its composition and properties,
the proposed modified PET is not necessarily a practically usable
molding material.
[0009] Further, it is extremely difficult to produce a good foamed
article by foam-extruding a linear aromatic polyester resin such as
polyethylene terephthalate, because the melt thereof is less
elasticity and viscous.
[0010] To solve the above problems, Japanese Patent Publication No.
5-15736 proposes to foam-extrude a mixture of a linear aromatic
polyester resin and a compound having two or more acid anhydride
groups per one molecule, and Japanese Patent Publication No.
5-47575 proposes to foam-extrude a mixture of a linear aromatic
polyester resin, a compound having two or more acid anhydride
groups and a specific metal compound. In addition, Japanese Patent
Application Laid-open No. 7-33899 proposes to foam-extrude a
polyester having a molecular weight distribution (weight-average
molecular weight/number-average molecular weight) of 5.0 to 21.0,
and Japanese Patent Application Laid-open No. 11-166067 proposes to
foam-extrude a polyester having a Z-average molecular weight of
1.times.10.sup.6 or higher and a branching parameter of 0.8 or
lower.
[0011] In any of the above-described methods, a polyfunctional
carboxylic anhydride or a polyfunctional glycidyl compound is added
to the polyester resin. If such a polyfunctional compound is added
during the production of the polyester resin, the resultant product
becomes three-dimensional to make it difficult to take out the
product from a reaction vessel. Therefore, the polyfunctional
compound or a branched aromatic copolyester resin obtained by
copolymerizing the polyfunctional compound with the linear
polyester resin must be added during the later extrusion step.
[0012] Japanese Patent Application Laid-open No. 8-231751 discloses
a foamed article made of an aromatic polyester resin which is
produced using a glycol component comprising cyclohexanedimethanol
and ethylene glycol. In this method, the crystallization during the
foaming process is delayed by the use of the aromatic polyester
resin made of two kinds of glycol components, so that the resultant
foamed article has uniform, fine closed cells, a high foaming
ratio, an excellent heat-insulating property, a high cushioning
property, and a good recycling ability. However, the foamed article
is still insufficient in the heat resistance and the mechanical
strength.
[0013] Further, Japanese Patent Application Laid-open No. 11-147969
proposes a foamed article made of an aromatic polyester resin which
is produced using a dicarboxylic acid component comprising
2,6-naphthalene dicarboxylic acid and terephthalic acid. In the
production of the foamed article, when the amount of
2,6-naphthalene dicarboxylic acid is increased to enhance the heat
resistance, the production of a satisfactory foamed article having
a high closed cell content becomes difficult because of the
increased crystallization rate.
SUMMARY OF THE INVENTION
[0014] In view of the above problems in the prior art, an object of
the present invention is to provide a polyester resin for films,
sheets and hollow containers having excellent heat resistance,
transparency, mechanical properties, moldability and fabrication
qualities. Another object of the present invention is to provide a
polyester resin having a high melt viscosity even when produced
without any branching agent, and further exhibiting a low intrinsic
viscosity, i.e., various excellent properties for producing foamed
articles even when polymerized in a short period of time.
[0015] As a result of extensive researches in view of the above
objects, the inventors have found that a copolyester which is
produced by using a limited amount of a specific glycol comonomer
and exhibits a specific solution viscosity, melt viscosity and
molecular weight distribution is excellent in heat resistance,
transparency, mechanical properties and fabrication qualities. The
inventors have further found that such a copolyester is excellent
suitable as a material for producing foamed articles.
[0016] Thus, the present invention provides a polyester resin
produced by polymerizing a monomer mixture comprising a glycol
component containing 5 to 60 mol % of a glycol (SPG) represented by
Formula I: 3
[0017] and 30 to 95 mol % of ethylene glycol, and a dicarboxylic
acid component containing 80 to 100 mol % of terephthalic acid
and/or an ester thereof; the polyester resin satisfying the
following requirements (1) to (4):
[0018] (1) an intrinsic viscosity of 0.4 to 1.5 dL/g when measured
at 25.degree.0 C. in a 6/4 by mass mixed solvent of
phenol/1,1,2,2-tetrachlo- roethane;
[0019] (2) a melt viscosity of 700 to 5,000 Pa.multidot.s when
measured at 240.degree. C. under a shear rate of 100 s.sup.-1;
[0020] (3) a molecular weight distribution of 2.5 to 12.0; and
[0021] (4) a glass transition temperature of 90.degree. C. or
higher, and a cooling crystallization exotherm peak of 5 J/g or
lower, when measured by a differential scanning calorimeter.
[0022] The present invention further provides a molded article
produced from the polyester resin.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The polyester resin of the present invention is produced by
polymerizing a monomer mixture comprising a glycol component (diol
component) containing 5 to 60 mol % of SPG represented by Formula I
and 30 to 95 mol % of ethylene glycol, and a dicarboxylic acid
component containing 80 to 100 mol % of terephthalic acid and/or an
ester thereof. Examples of the terephthalic acid esters include
dimethyl terephthalate, diethyl terephthalate, dipropyl
terephthalate, diisopropyl terephthalate, dibutyl terephthalate,
dicyclohexyl terephthalate, etc. With the use of SPG represented by
Formula I in the above range, the resultant polyester resin
simultaneously exhibits excellent heat resistance, solvent
resistance, transparency, moldability, mechanical properties and
fabrication qualities.
[0024] Preferably, the polyester resin of the present invention is
produced by polymerizing a monomer mixture comprising a diol
component containing 20 to 40 mol % of SPG represented by Formula I
and 50 to 80 mol % of ethylene glycol, and a dicarboxylic acid
component containing 95 to 100 mol % of terephthalic acid and/or an
ester thereof. By regulating the contents of the glycol component
and the dicarboxylic acid component within the above ranges, the
heat resistance and the mechanical properties can be further
enhanced.
[0025] The polyester resin particularly suitable for the production
of foamed articles is produced by polymerizing a monomer mixture
comprising a glycol component containing 15 to 60 mol % of SPG
represented by Formula I and 40 to 85 mol % of ethylene glycol, and
a dicarboxylic acid component containing 90 to 100 mol % of
terephthalic acid and/or an ester thereof.
[0026] In the present invention, the dicarboxylic acid component
may contain a dicarboxylic acid other than terephthahc acid and/or
its ester in an amount of 20 mol % or less. Examples of the
dicarboxylic acids other than terephthalic acid usable in the
present invention include isophthalic acid, phthalic acid,
2-methylterephthalic acid, naphthalenedicarboxylic acid,
biphenyldicarboxylic acid, tetralindicarboxylic acid, succinic
acid, glutaric acid, adipic acid, pimelic acid, suberic acid,
azelaic acid, sebacic acid, dodecanedicarboxylic acid,
cyclohexanedicarboxylic acid, decalindicarboxylic acid,
norbornanediacarboxylic acid, tricyclodecanedicarboxylic acid,
pentacylcododecanedicarboxylic acid, isophoronedicarboxylic acid,
3,9-bis(2-carboxyethyl)-2,4,8,10-tetraoxaspi- ro[5.5]undecane,
trimellitic acid, trimesic acid, pyromellitic acid, and
tricarballylic acid, although not limited thereto.
[0027] Also, in the present invention, the glycol component may
contain a glycol other than SPG represented by Formula I and
ethylene glycol in an amount of 10 mol % or less. Examples of such
a glycol include, but not limited to, an aliphatic diol such as
trimethylene glycol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, diethylene glycol, triethylene glycol, propylene
glycol and neopentyl glycol; a polyalkylene glycol such as
polyethylene glycol, polypropylene glycol and polybutylene glycol;
a three or more valent polyhydric alcohol such as glycerol,
trimethylol propane and pentaerythritol; an alicyclic diol such as
1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol,
1,2-decahydronaphthalenedimethanol,
1,3-decahydronaphthalenedimethanol,
1,4-decahydronaphthalenedimethanol,
1,5-decahydronaphthalenedimethanol,
1,6-decahydronaphthalenedimethanol,
2,7-decahydronaphthalenedimethanol, tetralindimethanol,
norbornanedimethanol, tricyclodecanedimethanol,
5-methylol-5-ethyl-2-(1,1-dimehyl-2-hydroxyethyl)-1,3-dioxane and
pentacylcododecanedimethanol; an alkylene oxide adduct of a
bisphenol such as 4,4'-(1-methylethylidene)bisphenol,
methylenebisphenol (bisphenol F), 4,4'-cyclohexylidenebisphenol
(bisphenol Z) and 4,4'-sulfonylbisphenol (bisphenol S); and an
alkylene oxide adduct of an aromatic dihydroxy compound such as
hydroquinone, resorcin, 4,4'-dihydroxybiphenyl,
4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxydiphenyl
benzophenone.
[0028] The polyester resin of the present invention may be produced
by any suitable known method without particular limitations. For
example, the polyester resin may be produced by transesterification
or direct esterification which may be conducted in either a melt
polymerization method or a solution polymerization method. As a
transesterification catalyst, an esterification catalyst, an
etherification inhibitor, a polymerization catalyst, various
stabilizers such as a heat stabilizer and a light stabilizer and a
polymerization modifier, those known in the polymer art are used.
Examples of the transesterification catalyst include compounds of
manganese, cobalt, zinc, titanium, and calcium. Examples of the
esterification catalyst include compounds of manganese, cobalt,
zinc, titanium, and calcium. Examples of the etherification
inhibitor include amine compounds.
[0029] Examples of the polycondensation catalyst include compounds
of germanium, antimony, tin, and titanium. Examples of the heat
stabilizer include various phosphorus compounds such as phosphoric
acid, phosphorous acid and phenylphosphonic acid. In addition,
various additives such as a light stabilizer, an antistatic agent,
a lubricant, an antioxidant and a mold-release agent may be used in
the production of the polyester resin.
[0030] SPG may be added at any stage of producing the polyester
resin. For example, SPG may be added after completion of the
esterification reaction or transesterification reaction. In the
direct esterification method, water may be used to keep the slurry
condition stable.
[0031] In the present invention, the properties of the polyester
resin were measured by the following methods.
[0032] (1) Intrinsic viscosity (IV)
[0033] The intrinsic viscosity was measured using an Ubbelohde
viscometer at a constant temperature of 25.degree. C. in a 6:4 by
mass mixed solvent of phenol and 1,1,2,2-tetrachloroethane.
[0034] (2) Melt viscosity
[0035] The melt viscosity was measured using Capirograph 1C
available from Toyo Seiki Co., Ltd. under the following
conditions.
[0036] Measuring temperature: 240.degree. C.;
[0037] Preheating time: 1 min
[0038] Nozzle diameter: 1 mm
[0039] Nozzle length: 10 mm
[0040] Shear rate: 100 s.sup.-1
[0041] (3) Molecular weight distribution (Mw/Mn)
[0042] Measuring device: gel permeation chromatograph (GPC)
"Shodex-11" available from Showa Denko Co., Ltd.
[0043] Solvent: 2 mmol/L sodium trifluoroacetate in
hexafluoro-2-propanol
[0044] Specimen concentration: about 0.05 wt %
[0045] Detector: Refractive Index Detector (RI)
[0046] Calibration: Polymethyl methacrylate (PMMA) standard
[0047] (4) Drop-weight test
[0048] Measuring device: Drop-weight tester available from Parker
Corporation
[0049] Environmental conditions: 25.degree. C. and 60.+-.20%
relative humidity
[0050] Shape of weight: Semispherical head of 20 mm diameter
[0051] Dropping speed: 10 m/s
[0052] Impact energy: 300 J
[0053] The energy absorbed when the weight penetrated through the
test specimen was measured under the above conditions according to
ASTM D3029. Using the measured result, the drop-weight breaking
strength was calculated from the following formula:
Drop-weight breaking strength=(absorbed energy)/(thickness of test
specimen)
[0054] (5) Glass transition temperature and cooling crystallization
exotherm peak
[0055] Using DSC/TA-50WS available from Shimadzu Corporation, about
10 mg of a sample polymer were placed in an unsealed aluminum
container and heated at a temperature rise rate of 20.degree.
C./min in a nitrogen gas flow of a flow rate of 30 mL/min to
measure the glass transition temperature (Tg). The temperature at
the center of the discontinuous region of the base line on the DSC
curve, i.e., the temperature at which the specific heat is reduced
to half was employed as Tg. After the measurement of Tg, the sample
polymer was kept at 280.degree. C. for one minute, and then, cooled
at a temperature drop rate of 10.degree. C./min. The cooling
crystallization exotherm peak (hereinafter referred to merely as
".DELTA.Hc") was determined as the area of an exotherm peak which
appeared during the cooling.
[0056] The polyester resin of the present invention has an
intrinsic viscosity of 0.4 to 1.5 dL/g, preferably 0.5 to 1.0 dL/g,
more preferably 0.6 to 0.8 dL/g. When the intrinsic viscosity is
0.4 dL/g or higher, the resultant molded article is excellent in
strength, and when the intrinsic viscosity is 1.5 dL/g or lower,
the polyester resin is excellent in moldability.
[0057] The polyester resin of the present invention has a melt
viscosity of 700 to 5,000 Pa.multidot.s when measured at
240.degree. C. under a shear rate of 100 s.sup.-1. When the melt
viscosity lies within the above range, the polyester resin is
excellent in moldability.
[0058] The polyester resin of the present invention has a molecular
weight distribution of 2.5 to 12.0. When the molecular weight
distribution lies within the above-specified range, the polyester
resin is excellent in moldability. The molecular weight
distribution means a ratio (Mw/Mn) of weight-average molecular
weight (Mw) to number-average molecular weight (Mn). The molecular
weight distribution can be regulated within the range of 2.5 to
12.0 by appropriately selecting the addition amount and addition
timing of SPG, the molecular weight of the polyester, the
polymerization temperature and the additives.
[0059] The impact strength of the polyester resin of the present
invention is expressed by the drop-weight breaking strength. The
drop-weight breaking strength is 10 kJ/m or higher when vertically
applying an impact energy of 300 J to a polyester sheet made of the
polyester resin by dropping a weight having a semispherical head of
20 mm diameter. When the drop-weight breaking strength is 10 kJ/m
or higher, the resultant molded article shows a practically
effective impact strength.
[0060] The polyester resin of the present invention has a glass
transition temperature of 90.degree. C. or higher and a cooling
crystallization exotherm peak of 5 J/g or lower when measured by a
differential scanning calorimeter (DSC). When the glass transition
temperature is 90.degree. C. or higher, the polyester resin
exhibits a practically effective heat resistance. Also, when the
cooling crystallization exotherm peak is 5 J/g or lower, the
polyester resin is excellent in transparency, moldability and
fabrication qualities.
[0061] The polyester resin of the present invention is formed into
shaped article required to have a high transparency, for example,
formed into non-stretched or slightly stretched single- or
multi-layer sheets by T-die extrusion or co-extrusion, which may be
fabricated into stretched films or slightly stretched deep-drawn
containers; and thin-wall hollow containers having a body thickness
of 0.1 to 2 mm by non-stretch direct blow molding or stretch blow
molding.
[0062] The sheets obtained from the polyester resin of the present
invention may be used in various applications. In the building
material use, the sheets may be used as exterior materials such as
illumination boards for vending machines, show-cases, outdoor sign
boards and carports; covers for various industrial machines;
windscreens; and factory partition boards. The application to home
electric appliances includes electric lamp covers, front screen
panels for projection TV, back light-guiding plates and front
panels for game devices. In the food application, the sheets may be
used as transparent containers to be pasteurized or sterilized,
heat-resistant transparent drinking cups, food trays, and lids for
lunch box to be re-heated. Further, the polyester resin sheets are
applicable to clear cases and clear boxes fabricated by folding,
blisters and export products of a long term shipping beyond the
equator. The sheets or hollow containers obtained from the
polyester resin of the present invention are also used, for
example, as packaging or wrapping materials.
[0063] The foamed article of the present invention is produced by
foaming the polyester resin and then stabilizing the foamed
structure. The method for foaming the polyester resin is not
particularly limited and may be mainly performed by heating a resin
impregnated with a foaming agent, or by kneading a foaming agent
into a molten resin. The polyester resin may be foam-molded by an
in-mold foaming method or a foaming extrusion method, though not
limited thereto. The "in-mold foaming" means a method of foaming
the resin into beads and then molding in a mold under heating to
produce blocks.
[0064] Preferably, the foamed article of the present invention is
produced by melting the resin under high temperatures and high
pressures, mixing a foaming agent with the molten resin, and
extruding the molten resin to a low-pressure region for foaming.
Examples of the foaming agent include inert gases, saturated
aliphatic hydrocarbons, aromatic hydrocarbons, halogenated
hydrocarbons, ethers and ketones. These foaming agents may be used
alone or in combination of two or more. Specific examples of the
foaming agent include carbon dioxide gas, nitrogen gas, methane,
ethane, n-butane, isopentane, neopentane, n-hexane,
2-methylpentane, 3-methylpentane, 2,2-dimethylbutane,
2,3-dimethylbutane, methylcyclopropane, ethylcyclobutane,
1,1,2-trimethylcyclopropane, benzene, trichloromonofluoromethane,
trichlorotrifluoroethane, dichlorotetrafluoroethane, dimethyl
ether, 2-ethoxyethanol, acetone, ethyl methyl ketone and acetyl
ketone. The foaming agent is used in an amount of 1 to 20 parts by
weight based on 100 parts by weight of the polyester resin. When
the amount of the foaming agent is less than 1 part by weight, the
polyester resin is insufficiently foamed, resulting in poor cost
performance and foamed articles of poor heat insulation. When the
amount of the foaming agent is more than 20 parts by weight, it is
not possible to achieve stable gas seal at the dies, resulting in
production of poor foamed article.
[0065] In general, the extrusion foaming is conducted by mixing a
foaming agent with a molten resin, and cooling the molten resin to
a temperature at which the viscosity of the resin reaches a
suitable level for foaming. Therefore, it is desirable to
sufficiently melt-knead the polyester resin and the foaming agent
at a high rotation speed. In addition, in view of enhancing the
cooling efficiency, the kneaded product is preferred to be extruded
at a low screw rotation speed to control the shear-heating as low
as possible. If the melt-kneading and the cooling for foaming are
performed in the same extruder, the extruder is required to operate
at a low screw rotation speed for ensuring a sufficient cooling of
the resin. As a result, the melt-kneading of the polyester resin
and the foaming agent tends to become insufficient, thereby causing
poor foaming and poor productivity due to low extrusion amount.
Accordingly, in the present invention, the melt-kneading of the
molten polyester resin with the foaming agent and the cooling prior
to extruding the resin into a low-pressure region for foaming are
preferred to be separately conducted in respective one or more
extruders. The configurations or types of the extruders are not
particularly restricted.
[0066] In the production of the foamed article of the present
invention, the polyester resin may be added with a suitable
additive, for example, a nucleating agent such as talc, a
cross-linking agent such as ionomer, an inorganic filler including
fibers, a flame retardant, an antistatic agent, an antioxidant and
a colorant.
[0067] The foamed article of the present invention obtained by the
above process preferably has a thickness of 0.2 to 7 mm. When the
thickness is less than 0.2 mm, the heat insulation, the cushioning
property and the mechanical strength are possibly insufficient.
When the thickness is more than 7 mm, the fabrication qualities
such as thermoforming and bag making are possibly poor.
[0068] The present invention will be described in more details by
reference to the following examples. However, it should be noted
that the following examples are illustrative and not intended to
limit the invention thereto.
[0069] In the following examples and comparative examples, dimethyl
terephthalate is abbreviated to "DMT", dimethyl
2,6-naphthalenedicarboxyl- ate to "NDCM", pyromellitic acid to
"PMDA", ethylene glycol to "EG", neopentyl glycol to "NPG",
1,4-cyclohexanedimethanol to "CHDM", and
3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,
10-tetraoxaspiro[5.5]undecane to "SPG".
EXAMPLE 1
[0070] (1) Production of resin
[0071] A mixture of 13,313 g (69 mol) of DMT, 7,191 g (116 mol) of
EG and 2,294 g (7.5 mol) of SPG was heated to 200.degree. C. in
nitrogen atmosphere in the presence of manganese acetate
tetrahydrate in an amount of 0.03 mol based on 100 mol of DMT to
conduct a transesterification reaction.
[0072] After the amount of methanol distilled reached 90% or higher
the stoichiometric amount, 0.01 mol of antimony (III) oxide and
0.06 mol of triphenyl phosphate (hereinafter referred to merely as
"TPP"), each based on 100 mol of DMT, were added to the reaction
mixture. The temperature was gradually raised and the pressure was
gradually reduced to finally reach 280.degree. C. and 0.1 kPa or
lower to conduct a polymerization. The polymerization was
terminated when the reaction product reached a predetermined melt
viscosity, thereby obtaining a polyester containing SPG unit in an
amount of 9 mol % (SPG9). The content of SPG unit in the polymer
was measured by .sup.1H-NMR (400 MHz).
[0073] (2) Preparation of injection-molded article
[0074] The polyester thus obtained was vacuum-dried under
predetermined conditions and injection-molded under predetermined
conditions using a screw injection molding machine (screw diameter:
32 mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens
of 3.2 mm thick. The results of measurement for various properties
of the injection-molded test specimens are shown in Table 1.
[0075] (3) Preparation of sheet
[0076] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick. The test results are shown in Table 2.
EXAMPLE 2
[0077] (1) Production of resin
[0078] A polyester composed of a glycol component containing 20 mol
% of SPG unit and 80 mol % of ethylene glycol unit, and a
dicarboxylic acid component containing 100 mol % of terephthalic
acid unit (SPG20) was prepared in the same manner as in Example
1.
[0079] (2) Preparation of injection-molded article
[0080] The polyester thus obtained was vacuum-dried under
predetermined conditions and injection-molded under predetermined
conditions using a screw injection molding machine (screw diameter:
32 mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens
of 3.2 mm thick. The results of measurement for various properties
of the injection-molded test specimens are shown in Table 1.
[0081] (3) Preparation of sheet
[0082] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick. The test results are shown in Table 2.
EXAMPLE 3
[0083] (1) Production of resin
[0084] A polyester composed of a glycol component containing 50 mol
% of SPG unit and 50 mol % of ethylene glycol unit, and a
dicarboxylic acid component containing 100 mol % of terephthalic
acid unit (SPG50) was prepared in the same manner as in Example
1.
[0085] (2) Preparation of injection-molded article
[0086] The polyester thus obtained was vacuum-dried under
predetermined conditions and injection-molded under predetermined
conditions using a screw injection molding machine (screw diameter:
32 mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens
of 3.2 mm thick. The results of measurement for various properties
of the injection-molded test specimens are shown in Table 1.
[0087] (3) Preparation of sheet
[0088] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick. The test results are shown in Table 2.
EXAMPLE 4
[0089] (1) Production of resin
[0090] A polyester composed of a glycol component containing 5 mol
% of SPG unit and 95 mol % of ethylene glycol unit, and a
dicarboxylic acid component containing 90 mol % of terephthalic
acid unit and 10 mol % of naphthalenedicarboxylic acid unit
(SPG5N10) was prepared in the same manner as in Example 1.
[0091] (2) Preparation of injection-molded article
[0092] The polyester thus obtained was vacuum-dried under
predetermined conditions and injection-molded under predetermined
conditions using a screw injection molding machine (screw diameter:
32 mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens
of 3.2 mm thick. The results of measurement for various properties
of the injection-molded test specimens are shown in Table 1.
[0093] (3) Preparation of sheet
[0094] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick. The test results are shown in Table 2.
[0095] The injection-molded articles and sheets were evaluated by
the following methods.
[0096] 1. Evaluation of injection-molded article
[0097] (1) Tensile properties
[0098] Measured according to ASTM D638.
[0099] (2) Flexural properties
[0100] Measured according to ASTM D790.
[0101] (3) Deflection temperature under load
[0102] Measured according to ASTM D648 under a bending stress of
451 kPa.
[0103] (4) Drop-weight impact test
[0104] Measuring device: Drop-weight impact tester available from
Parker Corporation
[0105] Environmental conditions: 25.degree. C. and 60.+-.20%
relative humidity
[0106] Shape of weight: Semi-spherical head having a 20 mm
diameter
[0107] Dropping speed: 10 m/s
[0108] Impact energy: 300 J
[0109] The energy absorbed when the weight penetrated through the
test specimen was measured under the above conditions according to
ASTM D3029. Using the measured result, the drop-weight breaking
strength was calculated from the following formula:
Drop-weight breaking strength=(absorbed energy)/(thickness of test
specimen)
[0110] 2. Evaluation of sheet
[0111] (1) Moldability
[0112] The molded sheet was cut into square test specimens of 100
mm in length (extrusion direction).times.100 mm in width (width
direction). The thicknesses of the test specimen were measured at
ten points arbitrarily selected. The moldability was ranked "good"
when the standard deviation was within 5% of the average thickness,
and "poor" when exceeding 5%. Further, the resin which was
difficult to extrude into sheet was also ranked "poor".
[0113] (2) Heat resistance
[0114] The sheet was cut into square test specimens of 100 mm in
length (extrusion direction).times.100 mm in width (width
direction). The test specimens were heated at 85.degree. C. for 30
minutes in an oven. The test specimens exhibiting a shrinkage of
more than 10% in each of lengthwise and widthwise directions were
ranked "poor" in the heat resistance.
[0115] (3) Drop-weight impact test
[0116] Measuring device: falling weight impact tester available
from Parker Corporation
[0117] Environmental conditions: temperature: 25.degree. C.;
relative humidity: 60.+-.20%
[0118] Shape of weight: semi-spherical head having a diameter of 20
mm
[0119] Falling weight impact velocity: 10 m/s
[0120] Impact energy: 300 J
[0121] The energy absorbed when the weight penetrated through the
test specimen was measured under the above conditions according to
ASTM D3029. Using the measured result, the drop-weight breaking
strength was calculated from the following formula:
Drop-weight breaking strength=(absorbed energy)/(thickness of test
specimen)
[0122] Evaluation Standards
[0123] A: >40 kJ/m
[0124] B: 10 to 40 kJ/m
[0125] C: <10 kJ/m
[0126] (4) Punching quality
[0127] Pressing machine: TORC-PAC PRESS
[0128] Punching diameter: 19 mm.phi.
[0129] Blade: Thomson blade
[0130] The punching test was conducted under the above conditions
to evaluate the punching quality of each test specimen according to
the following standards:
[0131] A: completely punched, and no burr on cut surface
[0132] B: punchable, but burrs were present on cut surface
[0133] C: not punchable
1 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Polyester Resin Monomer
dicarboxylic acid component (molar ratio) DMT 100 100 100 --
DMT/NDCM -- -- -- 90/10 glycol component (molar ratio) SPG/EG 9/91
20/80 50/50 5/95 Tg (.degree. C.) 92 97 112 92 .DELTA.Hc (J/g) 4.0
0 0 0 IV (dL/g) 0.75 0.75 0.70 0.70 Molecular weight distribution
3.0 4.0 6.3 3.0 Melt viscosity (Pa .multidot. s) 800 1500 2500 850
Evaluation of injection-molded article Deflection temperature under
load 81 86 101 82 (.degree. C.) Tensile strength (MPa) 56 54 58 56
Elongation at break (%) 200 180 100 220 Flexural strength (MPa) 88
86 86 87 Flexural modulus (GPa) 2.4 2.7 2.5 2.5 Drop-weight
breaking strength 55 58 40 56 (kJ/m)
[0134]
2 TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Polyester Resin Monomer
dicarboxylic acid component (molar ratio) DMT 100 100 100 --
DMT/NDCM -- -- -- 90/10 glycol component (molar ratio) SPG/EG 9/91
20/80 50/50 5/95 Tg (.degree. C.) 92 97 112 92 .DELTA.Hc (J/g) 4 0
0 0 IV (dL/g) 0.75 0.75 0.70 0.7 Molecular weight distribution 3.0
4.0 6.3 3.0 Melt viscosity (Pa .multidot. s) 800 1500 2500 850
Evaluation of sheet Moldability good good good good Heat resistance
good good good good Impact strength A A A A Punching quality A A A
A
COMPARATIVE EXAMPLE 1
[0135] (1) Production of resin
[0136] A polyester composed of a glycol component containing 3 mol
% of SPG unit and 97 mol % of ethylene glycol unit, and a
dicarboxylic acid component containing 100 mol % of terephthalic
acid unit (SPG3) was prepared in the same manner as in Example
1.
[0137] (2) Preparation of injection-molded article
[0138] The polyester thus obtained was vacuum-dried under
predetermined conditions and injection-molded under predetermined
conditions using a screw injection molding machine (screw diameter:
32 mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens
of 3.2 mm thick. The results of measurement for various properties
of the injection-molded test specimens are shown in Table 3.
[0139] (3) Preparation of sheet
[0140] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick.
[0141] The test results are shown in Table 4.
COMPARATIVE EXAMPLE 2
[0142] (1) Polyester resin
[0143] PETG (33 mol % cyclohexanedimethanol-modified PET available
from Eastman Kodak Company as the trade name of EASTAR PETG 6763)
was used as the polyester resin.
[0144] (2) Preparation of injection-molded article
[0145] The polyester was vacuum-dried under predetermined
conditions and injection-molded under predetermined conditions
using a screw injection molding machine (screw diameter: 32
mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens of
3.2 mm thick. The results of measurement for various properties of
the injection-molded test specimens are shown in Table 3.
[0146] (3) Preparation of sheet
[0147] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick. The test results are shown in Table 4.
COMPARATIVE EXAMPLE 3
[0148] (1) Production of resin
[0149] A polyester composed of a glycol component containing 45 mol
% of SPG unit and 55 mol % of ethylene glycol unit, and a
dicarboxylic acid component containing 100 mol % of terephthalic
acid unit (SPG45) was prepared in the same manner as in Example
1.
[0150] (2) Preparation of injection-molded article
[0151] The polyester thus obtained was vacuum-dried under
predetermined conditions and injection-molded under predetermined
conditions using a screw injection molding machine (screw diameter:
32 mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens
of 3.2 mm thick. The results of measurement for various properties
of the injection-molded test specimens are shown in Table 3.
[0152] (3) Preparation of sheet
[0153] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick. The test results are shown in Table 4.
COMPARATIVE EXAMPLE 4
[0154] (1) Production of resin
[0155] A polyester composed of a glycol component containing 70 mol
% of SPG unit and 30 mol % of ethylene glycol unit, and a
dicarboxylic acid component containing 100 mol % of terephthalic
acid unit (SPG70) was prepared in the same manner as in Example
1.
[0156] (2) Preparation of injection-molded product
[0157] The polyester thus obtained was vacuum-dried under
predetermined conditions and injection-molded under predetermined
conditions using a screw injection molding machine (screw diameter:
32 mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens
of 3.2 mm thick. The results of measurement for various properties
of the injection-molded test specimens are shown in Table 3.
[0158] (3) Preparation of sheet
[0159] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick. The test results are shown in Table 4.
COMPARATIVE EXAMPLE 5
[0160] (1) Production of resin
[0161] A polyester composed of a glycol component containing 10 mol
% of SPG unit and 90 mol % of ethylene glycol unit, and a
dicarboxylic acid component containing 100 mol % of terephthalic
acid unit (SPG10) was prepared in the same manner as in Example
1.
[0162] (2) Preparation of injection-molded article
[0163] The polyester thus obtained was vacuum-dried under
predetermined conditions and injection-molded under predetermined
conditions using a screw injection molding machine (screw diameter:
32 mm.phi.; mold clamping force: 9.8 kN) to prepare test specimens
of 3.2 mm thick. The results of measurement for various properties
of the injection-molded test specimens are shown in Table 3.
[0164] (3) Preparation of sheet
[0165] The polyester was vacuum-dried under predetermined
conditions and extruded under predetermined conditions into a sheet
of about 0.8 mm thick. The test results are shown in Table 4.
3 TABLE 3 Com. Com. Com. Com. Com. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5
Polyester Resin Monomer dicarboxylic acid component (molar ratio)
DMT 100 100 100 100 100 glycol component (molar ratio) SPG/EG 3/97
-- 45/55 70/30 10/90 CHDM/EG -- 33/67 -- -- -- Tg (.degree. C.) 85
83 100 125 92 .DELTA.Hc (J/g) 38 0 0 0 3.0 IV (dL/g) 0.65 0.75 0.35
0.75 0.58 Molecular weight 2.2 2.7 2.6 13.5 2.3 distribution Melt
viscosity (Pa .multidot. s) 500 1000 550 6200 600 Evaluation of
injection- molded article Deflection temperature 75 73 91 112 82
under load (.degree. C.) Tensile strength (MPa) 56 44 58 56 50
Elongation at break (%) 200 240 4 9 160 Flexural strength (MPa) 84
68 86 67 81 Flexural modulus (GPa) 2.4 1.9 2.5 2.1 1.9 Drop-weight
breaking 55 44 4 5 6 strength (kJ/m)
[0166]
4 TABLE 4 Com. Com. Com. Com. Com. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5
Polyester Resin Monomer dicarboxylic acid component (molar ratio)
DMT 100 100 100 100 100 glycol component (molar ratio) SPG/EG 3/97
-- 45/55 70/30 10/90 CHDM/EG -- 33/67 -- -- -- Tg (.degree. C.) 85
83 100 125 92 .DELTA.Hc (J/g) 38 0 0 0 3.0 IV (dL/g) 0.65 0.75 0.35
0.75 0.58 Molecular weight 2.2 2.7 2.6 13.5 2.3 distribution Melt
viscosity (Pa .multidot. s) 500 1000 550 6200 600 Evaluation of
sheet Moldability poor good poor poor poor Heat resistance poor
poor good good good Impact strength A B C C C Punching quality C A
B C C
EXAMPLES 5 to 6 AND COMPARATIVE EXAMPLES 6 to 9
[0167] (1) Production of bottle
[0168] Respective resins shown in Tables 5 and 6 were molded into
bottles.
[0169] Molding conditions
[0170] Preform: 30 g
[0171] Injection molding machine: M200 available from Meiki
Seisakusho Co., Ltd.
[0172] Bottle: 330 mL capacity; pressure-proof type; petaloid
bottom
[0173] Blow molding machine: LB-01 available from Krupp Corpoplast
Maschinenbau GmbH
[0174] In COMPARATIVE EXAMPLE 6, polyethylene terephthalate (RT543
available from Nippon Unipet Co., Ltd.) having an intrinsic
viscosity of 0.75 dL/g was used.
[0175] The blow moldability of each resin was evaluated according
to the following standards:
[0176] Good: substantially no uneven thickness
[0177] Poor: uneven thickness along circumferential direction
[0178] (2) Falling test
[0179] A bottle filled with water was kept at 5.degree. C.
overnight, and then dropped by gravity with its bottom downward
(vertical drop). Fifteen bottles per each sample were subjected to
the falling test, and evaluated according to the following
standards:
[0180] Good: no change occurred
[0181] Poor: cracks or water leakage occurred
[0182] (3) Hot water filling test
[0183] A bottle filled with hot water of 85.+-.1.degree. C. was
allowed to stand overnight, and the heat resistance was evaluated
based on retention of height and capacity according to the
following standards:
[0184] Height retention:
[0185] Good: 99% or higher
[0186] Poor: less than 99%
[0187] Capacity retention:
[0188] Good: 98.5% or larger
[0189] Poor: less than 98.5%
[0190] The results are shown in Tables 5 and 6.
5 TABLE 5 Ex. 5 Ex. 6 Polyester Resin Monomer dicarboxylic acid
component (molar ratio) DMT -- 100 DMT/NDCM 95/5 -- glycol
component (molar ratio) SPG/EG 25/75 50/50 Tg (.degree. C.) 105 112
.DELTA.Hc (J/g) 0 0 IV (dL/g) 0.70 0.7 Molecular weight
distribution 4.0 6.3 Melt viscosity (Pa .multidot. s) 2000 2500
Evaluation of bottle Blow moldability good good Heat resistance
retention of height good good retention of capacity good good
Falling test good good
[0191]
6 TABLE 6 Com. Com. Com. Com. Ex. 6 Ex. 7 Ex. 8 Ex. 9 Polyester
Resin Monomer dicarboxylic acid component (molar ratio) DMT 100 100
100 100 glycol component (molar ratio) SPG/EG 0/100 3/97 45/55
70/30 Tg (.degree. C.) 82 83 100 125 .DELTA.Hc (J/g) 38 31 0 0 IV
(dL/g) 0.75 0.65 0.35 0.70 Molecular weight distribution 2.4 2.2
2.6 13.5 Melt viscosity (Pa .multidot. s) 480 500 550 6200
Evaluation of bottle Blow moldability good poor good poor Heat
resistance retention of height poor poor good good retention of
capacity poor poor good good Failling test good good poor poor
EXAMPLES 7 to 8 and COMPARATIVE EXAMPLES 10 to 13
[0192] (1) Extrusion of sheet
[0193] DMT, DMT-NDCM mixture or DMT-PMDA mixture as a dicarboxylic
component, and EG, SPG-EG mixture, CHDM-EG mixture or NPG-EG
mixture as a diol component were polycondensed in respective molar
ratios shown in Tables 7 and 8 to produce a polyester resin. Then,
0.05 part by weight of talc as a nucleating agent was added to 100
parts by weight of the polyester resin. The resultant resin
material was fed into a first extruder for melt-kneading, and
heated, melted and kneaded therein. Then, isobutane as a foaming
agent was fed under pressure into the extruder in an amount of 10
parts by weight based on 100 parts by weight of the polyester
resin, and the mixture was melt-kneaded. The melt-kneaded product
was fed to a second extruder, and then extruded through a ring die
at a tip end of the extruder at temperatures shown in Tables 7 and
8. The extruded tubular foamed article was drawn over a mandrel for
cooling, and cut along the extrusion direction to obtain a foamed
sheet. The moldability of the foamed sheet and properties of the
resin are shown in Tables 7 and 8. The properties of the polymers
were measured by the following methods. In Comparative Example 13,
the foam extrusion was difficult because of the formation of
three-dimensional polymer (gelation).
[0194] (2) Heat resistance test
[0195] The foamed sheet was cut into square test specimens of 100
mm in length (extrusion direction).times.100 mm in width (width
direction). The test specimens were heated at 85.degree. C. for 30
minutes in an oven. The test specimens exhibiting a shrinkage of
more than 10% in each of lengthwise and widthwise directions were
ranked "poor" in the heat resistance.
[0196] (3) Cell structure
[0197] The foamed sheet obtained in each of the examples and
comparative examples was cut into square pieces of 25 mm in length
and 25 mm in width without changing the thickness. Twenty square
pieces were stacked in the thickness direction to prepare a sample
for measuring a closed cell content (%). First, an apparent volume
Va (cm.sup.3) of the sample was determined from the outer
dimensions. Then, an actual volume Vx (cm.sup.3) of the sample was
measured by an air-pycnometer method according to ASTM D2856. Based
on the obtained Va and Vx, the open cell content Fo (%) was
calculated from the following formula:
Fo=(Va-Vx)/Va.times.100.
[0198] The closed cell content Fc (%) was calculated from the
following formula:
Fc=100-Fo.
[0199] The cell structure was evaluated according to the following
criteria:
[0200] A: uniform and extremely fine cells and a closed cell
content Fc of 85% or higher
[0201] B: uniform and fine cells and a closed cell content Fc of
80% or higher but less than 85%
[0202] C: slightly non-uniform cells and a closed cell content Fc
of 50% or higher but less than 80%
[0203] Both the foamed sheets obtained in Examples 7 and 8 showed a
high closed cell content and, therefore, were successfully formed
into a well-angulated tray by a vacuum molding method. The results
are shown in Tables 7 and 8.
7 TABLE 7 Ex. 7 Ex. 8 Polyester Resin Monomer dicarboxylic acid
component (molar ratio) DMT 100 100 glycol component (molar ratio)
SPG/EG 45/55 20/80 Tg (.degree. C.) 110 95 IV (dL/g) 0.70 0.75 Melt
viscosity (Pa .multidot. s) 2400 2500 Evaluation of foamed sheet
Extrusion temperature (.degree. C.) 190 180 Cell structure A A Heat
resistance good good
[0204]
8 TABLE 8 Com. Com. Com. Com. Ex. 11 Ex. 12 Ex. 13 Ex. 14 Polyester
Resin Monomer dicarboxylic acid component (molar ratio) DMT 100 --
100 -- DMT/NDCM -- 25/75 -- -- DMT/PMDA -- -- -- 95/05 glycol
component (molar ratio) CHDM/EG 33/67 -- -- -- EG -- 100 -- 100
NPG/EG -- -- 30/70 -- Tg (.degree. C.) 81 110 75 -- IV (dL/g) 0.75
0.80 0.80 -- Melt viscosity (Pa .multidot. s) 1000 1100 1000 --
Evaluation of foamed sheet Extrusion temperature (.degree. C.) 170
180 170 -- Cell structure B C C -- Heat resistance poor good poor
--
[0205] The polyester resin of the present invention is excellent in
heat resistance, transparency, mechanical properties, moldability
and fabrication qualities and, therefore, suitable as resin
materials for films, sheets, hollow containers and foamed articles.
Molded articles produced from the polyester resin of the present
invention are industrially useful as food packaging materials,
building materials or the like.
* * * * *