Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-09-06
2003-10-28
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S275000, C528S286000, C528S302000, C524S401000, C524S414000, C524S416000, C524S417000, C524S433000
Reexamination Certificate
active
06639045
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of producing an aliphatic polyester and to an aliphatic polyester obtained by the method.
Polyolefins and aromatic polyesters which are now used in a wide variety of fields have a problem because of their lack in biodegradability. While aliphatic polyesters which are biodegradable polymers are attractive, known aliphatic polyesters have a problem that physical properties thereof are not satisfactory and production thereof requires relatively high costs.
For example, polyhydroxybutyrate produced by using microorganisms requires high production costs. In addition, because a difference between the melting point and the decomposition point of polyhydroxybutyrate is small, the polyhydroxybutyrate is apt to be decomposed during molding to cause problems of generation of odor and reduction of mechanical properties. Polycaprolactone, which is one of a few currently industrially produced aliphatic polyesters, has a problem because the melting point is as low as about 60° C. Polymers of hydroxycarboxylic acids, such as polylactic acid, have excellent biodegradability and are usable as topical absorbing material. However, they are only produced through complicated processes.
Aliphatic polyesters obtained by polycondensation of an aliphatic carboxylic acid compound (e.g. aliphatic carboxylic acid, ester or anhydride) and a glycol are known. Such polyesters, however, have a number average molecular weight of only several thousands and are ill-suited for the formation of films and fibers. Thus, methods have been proposed to increase the molecular weight of the aliphatic polyester by crosslinking with a diisocyanate or by using an additional comonomer such as a polyfunctional isocyanate. These methods, however, have a problem because a gel is apt to be formed or because additional process steps are required.
As an ester interchange catalyst for the production of aliphatic polyesters, titanium tetraisopropoxide is generally used. The known catalyst, however, is unsatisfactory with respect to the reaction rate of polyesterification and has an additional problem of coloring of the product. Furthermore, films or fibers prepared from the polyester have not satisfactory mechanical properties such as breaking elongation. With regard to the coloring of the polyester, U.S. Pat. No. 5,504,148 suggests the use of a phosphorus compound, particularly, polyphosphoric acid, as an anti-coloring agent. The use of phosphoric acid or polyphosphric acid, however, cannot sufficiently accelerate the polyesterification and, further, causes a problem of formation of by-products such as tetrahydrofuran derived from a diol.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an industrially applicable method which can produce an aliphatic polyester having a resistance to hydrolysis.
Another object of the present invention is to provide a method which can produce an aliphatic polyester having good mechanical properties and good color tone at a high reaction rate.
It is a further object of the present invention to provide an aliphatic polyester obtained by the above method.
In accomplishing the foregoing objects, there is provided in accordance with the present invention a method of producing an aliphatic polyester, comprising polycondensing a raw material selected from the group consisting of
(A1) mixtures of an aliphatic diol and at least one aliphatic dicarboxylic acid compound selected from the group consisting of aliphatic dicarboxylic acids, diesters of aliphatic dicarboxylic acids and aliphatic dicarboxylic acid anhydrides,
(A2) prepolymers of mixtures (A1),
(A3) oxycarboxylic acid compounds,
(A4) prepolymers of oxycarboxylic acid compounds (A3),
(A5) mixtures of (a) an aliphatic diol, (b) at least one aliphatic dicarboxylic acid compound selected from the group consisting of aliphatic dicarboxylic acids, diesters of aliphatic dicarboxylic acids and aliphatic dicarboxylic acid anhydrides and (c) at least one auxiliary compound selected from the group consisting of aliphatic compounds and aromatic compounds having at least two functional groups which are reactive with at least one of (a) and (b),
(A6) prepolymers of mixtures (A5),
(A7) mixtures of (d) at least one oxycarboxylic acid compound and (e) at least one auxiliary compound other than oxycarboxylic acid compounds selected from the group consisting of aliphatic compounds and aromatic compounds having at least two functional groups which are reactive with (d), and
(A8) prepolymers of mixtures (A7) in the presence of a metal-containing ester interchange catalyst and a phosphorus-containing co-catalyst selected from the group consisting of
(B1) organic phosphinic acids,
(B2) monoammonium salts of hydrogen-containing phosphoric acids,
(B3) monoammonium salts of hydrogen-containing polyphosphoric acids,
(B4) calcium salts of hydrogen-containing phosphoric acids,
(B5) calcium salts of hydrogen-containing polyphosphoric acids,
(B6) magnesium salts of hydrogen-containing phosphoric acids,
(B7) magnesium salts of hydrogen-containing polyphosphoric acids, and
(B8) diarylphosphinic acids
Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments to follow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
A method of producing an aliphatic polyester according to the present invention includes a step of subjecting a raw material to polycondensation. The raw material is selected from the following substances (A1) through (A6).
Raw material (A1) is a mixture of an aliphatic diol and at least one aliphatic dicarboxylic acid compound selected from aliphatic dicarboxylic acids, diesters of aliphatic dicarboxylic acids and aliphatic dicarboxylic acid anhydrides. The aliphatic dicarboxylic acid compound may be represented by the following formula (1) or (2):
R
11
OOC—R
1
—COOR
11
(1)
wherein R
1
represents a divalent aliphatic group having 1-12 carbon atoms, preferably 1-10 carbon atoms, and R
11
represents a hydrogen atom, a lower alkyl group or an aryl group.
The divalent aliphatic group R
1
may be cyclic or linear and may be saturated or unsaturated. The divalent aliphatic group may contain a hetero atom such as oxygen. Illustrative of the divalent aliphatic groups are an alkylene group which may contain an ether linkage, an alkenylene group which may contain an ether linkage, an alkyleneoxy group and an oxyalkylene group. Specific examples of the divalent aliphatic groups include —CH
2
—, —C
2
H
4
—, —CH
2
O—, —CH
2
OCH
2
—, —C
3
H
6
—, —C
4
H
8
—, —C
6
H
12
—, —C
8
H
16
—, —C
12
H
24
— and —C
12
H
22
—.
The lower alkyl group R
11
may have 1-6 carbon atoms, preferably 1-4 carbon atoms. The aryl group R
11
may have 6-10 carbon atoms, preferably 6-8 carbon atoms, such as phenyl.
Illustrative of the aliphatic dicarboxylic acid compounds are succinic acid, adipic acid, sebacic acid, suberic acid, dodecanoic acid, diglycolic acid and acid anhydrides thereof.
The aliphatic diol to be used in conjunction with the above aliphatic dicarboxylic acid compounds may be represented by the following-formula (3):
HO—R
2
—OH
wherein R
2
represents a divalent aliphatic group having 1-12 carbon atoms, preferably 2-10 carbon atoms, and R
11
represents a hydrogen atom, a lower alkyl group or an aryl group.
The divalent aliphatic group R
1
may be cyclic or linear and may be saturated or unsaturated. The divalent aliphatic group may contain a hetero atom such as oxygen. Illustrative of the divalent aliphatic groups are an alkylene group which may contain an ether linkage, an alkenylene group which may contain an ether linkage, an alkyleneoxy group and an oxyalkylene group. Specific examples of the divalent aliphatic groups include —CH
2
—, —C
2
H
4
—, —C
3
H
6
—, —C
4
H
8
—, —C
6
H
12
—, —C
8
H
16
—, —C
12
H
24
—, —C
12
H
22
— (dodecenyl), —C
6
H
10
— (cyclohexenyl), —CH
2
O— and —CH
2
OCH
2
—.
The aliphatic diol is generally used in an amount of 1-2 moles, preferably 1.02-1
Cao Amin
Masuda Takashi
Acquah Samuel A.
Lorusso, Loud & Kelly
National Institute of Advanced Industrial Science and Technology
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