Block copolyester

Details Block copolyester Block copolyester

2002-12-31

2003-12-30

Acquah, Samuel A. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C528S295300, C528S302000, C528S308000, C528S308600, C528S298000, C525S444000

Reexamination Certificate

active

06670429

ABSTRACT:

FIELD OF INVENTION
The present invention relates to a copolyester, and in particular to a block copolyester.
BACKGROUND
A known category of thermoplastic elastomers is polyester elastomers, which can be used in a wide range of applications such as in tubes, belts, or molded articles, made for example by injection molding. Such polyester elastomers normally contain a rigid, crystalline polyester (or “hard” segment), usually an aromatic polyester such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), which is modified with a non-crystalline material (or “soft” segment). The hard, crystalline segments are chemically linked with the soft, non-crystalline segments in a single polymeric chain. In this material, the hard segments congregate to form crystalline areas that provide strength and hardness to the material. Similarly, the soft segments congregate in a separate phase, and provide flexibility to the material. PBT is the most commonly used hard segment, because of its ease of crystallization. The soft segment is normally a polyether such as polytetramethylene glycol (PTMEG), polyethyleneglycol (PEG), polypropylene glycol (PPG), or ethylene oxide/propylene oxide block copolymers. The disadvantages of polyethers include their sensitivity to heat, oxidation and UV. Alternative soft segments include aliphatic polyesters such as adipate ester or polycaprolactone, which can be sensitive to hydrolysis. In addition, transesterification tends to occur during synthesis, which results in break up of the hard and/or soft segments with a consequential loss of the required properties. In particular, there is a requirement for a copolyester which possesses both high melting point and low glass transition point.
REVIEW OF THE PRIOR ART
U.S. Pat. No. 4,031,165-A claims a process of making block copolyesters in the presence of a titanium-type catalyst and a phosphorus compound.
GB-2203425-A is directed to dimerised fatty acids and describes forming polyesters using such dimerised fatty acids. The polyesters produced according to the teaching of GB-2203425-A are homo polyesters or random copolyesters.
JP-11080336-A discloses a copolyester having a non-crystalline part formed from dimer acid, terephthalic acid and polyoxyethylene glycol, and a crystalline part formed from butylene terephthalate.
SUMMARY OF THE INVENTION
We have now surprisingly discovered a block copolyester which reduces or substantially overcomes at least one of the aforementioned problems.
Accordingly, the present invention provides a block copolyester comprising a hard segment and a soft segment wherein the melting point of the copolyester is greater than or equal to 200° C., and the glass transition temperature of the copolyester is less than or equal to −40° C.
The invention also provides a block copolyester comprising a hard segment and a soft segment wherein the melting point of the copolyester is less than 20° C. lower than the melting point of the hard segment, and the glass transition temperature of the copolyester is less than 20° C. higher than the glass transition temperature of the soft segment.
The invention further provides a method of preparing a block copolyester as defined herein wherein the soft segment is formed in situ, in the presence of the preformed hard segment, and the same diol is used to form both the hard and soft segments.
The composition of the polyester hard segment may vary over a wide range. The polyester is preferably an aromatic polyester. Suitable aromatic dicarboxylic acids, and/or ester derivatives thereof, for use in forming the hard segment, include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, or mixtures thereof. Terephthalic acid, and/or ester derivative thereof, is particularly preferred. The hard segment is preferably formed from greater than 50, more preferably greater than 70, particularly greater than 90, and especially greater than 95 and up to 100 mole % of aromatic dicarboxylic acid(s) and/or ester derivatives thereof. The balance (up to 100 mole %) of dicarboxylic acids (if any) can be suitably made up of aliphatic dicarboxylic acids, such as adipic acid, sebacic acid, or cyclohexane dicarboxylic acid.
Suitable diols or glycols for use in forming the hard segment include aliphatic diols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, trimethylene glycol, tetramethylene glycol, and cyclohexane dimethanol, or aromatic diols such as 2,2-bis(4-hydroxyphenyl)propane. The hard segment is preferably formed from greater than 50, more preferably greater than 70, particularly greater than 90, and especially greater than 95 and up to 100 mole % of aliphatic glycol(s), preferably ethylene glycol and/or 1,4-butanediol.
In a particularly preferred embodiment of the invention, the hard segment is polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate or mixtures thereof, and especially polybutylene terephthalate.
The hard segment preferably has a molecular weight number average in the range from 1000 to 30,000, more preferably 2,000 to 15,000, particularly 2,500 to 10,000, and especially 3,000 to 5,000.
The hard segment preferably has a melting point (Tm) in the range from 200 to 280° C., more preferably 210 to 270° C., particularly 215 to 255° C., and especially 220 to 230° C.
The polyester soft segment is preferably an aliphatic polyester. The polyester is preferably formed from a dimer fatty acid and/or ester derivative thereof and/or dimer fatty diol.
The term dimer fatty acid is well known in the art and refers to the dimerisation product of mono- or polyunsaturated fatty acids. Preferred dimer acids are dimers of C
10
to C
30
, more preferably C
12
to C
24
, particularly C
14
to C
22
, and especially C
18
alkyl chains. Consequently, preferred dimer acids comprise in the range from 20 to 60, more preferably 24 to 48, particularly 28 to 44, and especially 36 carbon atoms. Suitable dimer fatty acids include the dimerisation products of oleic acid, linoleic acid, linolenic acid, palmitoleic acid, elaidic acid, or erucic acid. The dimerisation products of the unsaturated fatty acid mixtures obtained in the hydrolysis of natural fats and oils, e.g. sunflower oil, soybean oil, olive oil, rapeseed oil, cottonseed oil and tall oil, may also be used.
In addition to the dimer fatty acids, dimerisation usually results in varying amounts of oligomeric fatty acids (so-called “trimer”) and residues of monomeric fatty acids (so-called “monomer”), or esters thereof, being present. The amount of momomer can, for example, be reduced by distillation. Particularly preferred dimer fatty acids have a dicarboxylic (or dimer) content of greater than 95%, more preferably greater than 97.5%, particularly greater than 98.5%, and especially greater than 99.0% by weight.
The soft segment is preferably formed from greater than 50, more preferably greater than 70, particularly greater than 90, and especially greater than 95 and up to 100 mole % of dimer fatty acids and/or ester derivatives thereof. The balance (up to 100 mole %) of dicarboxylic acids (if any) can be suitably made up of non-dimeric fatty dicarboxylic acids and/or ester derivatives thereof. Preferred materials are linear dicarboxylic acids having terminal carboxyl groups having a carbon chain of from 6 to 20, more preferably 8 to 12 carbon atoms, such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, heptane dicarboxylic acid, octane dicarboxylic acid, nonane dicarcoxylic acid, decane dicarboxylic acid, undecane dicarboxylic acid, dodecane dicarboxylic acid and higher homologs thereof.
Suitable diols include those mentioned above, and at the same concentration ranges, for forming the hard segment. Alternatively, dimer fatty diols may be used, which can be produced by hydrogenation of the corresponding dimer acid. Thus, the soft segment is preferably formed from greater than 25, more preferably greater than 35, particularly greater than 45, and especially greater than 47.5 a

Affiliated with

Also associated with

Rating

Block copolyester does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Block copolyester, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Block copolyester will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3154488