Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-11-20
2002-09-24
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S279000, C528S287000, C528S481000, C528S491000
Reexamination Certificate
active
06455664
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a polyesters, and more particularly of polyesters derived from cycloaliphatic diols and cycloaliphatic esters and a process for their formation.
BACKGROUND OF THE INVENTION
Poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate), PCCD, is a known polyester referred to in U.S. Pat. No. 2,891,930 to Caldwell et al and U.S. Pat. No. 2,901,466 to Kibler et al. Kibler et al discusses poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) as one of the sixty-eight examples of linear polyesters and polyesteramides. According to Example 42, an excess amount of the glycol or 1,4-cyclohexanedimethanol component is utilized for making poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate). U.S. Pat. No. 4,327,206 to Winston et al describes the reaction of 1,4-cyclohexanedicarboxylate with aromatic diols.
U.S. Pat. No. 5,986,040 to Patel and Smith describes the production of PCCD having a melting point of the final moldable linear PCCD from 208 to 224 degrees as shown in Table 3 of the Examples.
Typically, molding compositions based upon blends of thermoplastic resin incorporating 1,4-cyclohexanedicarboxylic acid residues in the polymer chain may have good impact resistance, good processability, and transparency. U.S. Pat. No. 5,986,040 to Patel and Smith describes PCCD resins having those properties. Further and additional improvements to the properties, such as thermal capacity, are desirable.
SUMMARY OF THE INVENTION
The present invention is directed to an improved process for producing a moldable linear poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate), PCCD, resin having crystalline properties with an enhanced melting temperature that makes it suitable for polymer blends. By the improved process, the melting points of the PCCD is enhanced to about 225 to about 234 degrees Centigrade thereby improving the thermal capability and crystallinity of the resin.
Typically, the crystallinity of PCCD, is not as high as that of such commercially available polyesters as poly(1,4-butylene terephthalate), or “PBT” which is an ingredient of many resin blends, such as blends with polycarbonate and other thermoplastic polymers. In addition to imparting desirable molding characteristics, enhanced crystallinity imparts such advantageous properties as its resistance to solvents. Thus, it is desirable to enhance the crystallinity of poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) and produce a poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) with uniform melting properties which permit its incorporation into thermoplastic blends useful for weatherable molding type applications. Enhanced crystallinity results in a desirable higher melting temperature for a given degree of polymer polymerization.
For sake of clarity, the following Table 1 sets forth the meaning of the abbreviations used throughout the specification.
TABLE 1
Abbreviations
Abbreviation
Name
PCCD
1,4-cyclohexanedicarboxylic acid, polymer with
1,4-cyclohexanedimethanol (9CI Chemical Abstracts Index
name); also
poly(1,4-cyclohexylenedimethylene 1,4-
cyclohexanedicarboxylate)
CHDM
1,4-cyclohexanedimethanol (trans/cis mixture)
t-DMCD
dimethyl trans-1,4-cyclohexanedicarboxylate
TPT
tetrakis(2-isopropyl)orthotitanate; also titanium(IV)
isopropoxide
MV
Melt Viscosity
T
m
Melting Point
A linear cycloaliphatic polyester resin consists essentially of a polyester having the formula:
where R is an alkyl from 1 to 6 carbon atoms or residual endgroups derived from either monomer, and n is greater than about 70. The polyester is derived from the transesterification reaction of a starting DMCD and a starting CHDM.
DMCD and CHDM are polymerized to produce a low viscosity polymer intermediate PCCD with a melt viscosity of from about 50 to about 800 poise, preferably from about 200 to about 500 poise.
Next, the low viscosity intermediate is solid state polymerized at a temperature from about 175 C to about 210 C, preferably from about 190 C to about 206 C, to produce a resulting PCCD polymer having a melting temperature, T
m
, about 225 to about 234 degrees Centigrade having improved thermal capability due enhanced crystallinity of the resin.
The preferred enhanced melt viscosity of the final prepared PCCD is from about 2,000 to about 22,000 poise. For applications for extruding the resulting resin into a sheet form, the preferred melt viscosity is from about 7000 poise to about 22000 poise, and more preferably from about 10000 poise to about 18000 poise. For application for injection molding the resulting resin, the preferred melt viscosity is from about 1000 poise to about 10000 poise and more preferably from about 2000 to about 6000.
The starting CHDM and DMCD are reacted in the presence of a catalyst in an inert atmosphere to form the low viscosity PCCD polymer having ester end groups such as a carboxycyclohexanecarboxylate end group (or ester thereof) and acid or hydroxy end groups such as alkyoxycyclohexanealkyanol end groups. The low viscosity intermediate preferably has hydroxy end group to ester end group present in about a 1 to 1 ratio so that molecular weight may be increased by further polymerization of the oligomer. The intermediate is next further reacted for increasing the molecular weight of the PCCD. For the intermediate oligomer, the acid number which is determined by the number of acid end groups on the polymer chain is preferably less than about 10, preferable less than 6 meq/kg as determined from the titration method. Preferably the amount of catalyst present is less than about 200 ppm. Typically, catalyst may be present in a range from about 20 to about 300 ppm.
The starting CHDM has a trans-CHDM greater than the equilibrium amount and the reaction is carried out in an inert atmosphere under conditions to minimize trans to cis isomerization of said starting DMCD. These conditions require the starting DMCD and the starting CHDM to be present in a molar stoichiometric amount to a slight molar excess of DMCD so that the number of ester end groups such as acid or methyl carboxycyclohexanecarboxylate end groups and the number hydroxy end groups such as alkyoxycyclohexanealkyanol end groups are in substantially equal proportions for the low viscosity PCCD intermediate. The resulting low viscosity PCCD is then reacted to build molecular weight.
Also, in accordance with preferred conditions for preparing the PCCD oligomer, it is desirable to minimize the time period for forming the PCCD oligomer to prevent trans-to-cis isomerization. The utilization of a stoichiometric excess of diol or CHDM as a starting reactant slows the reaction rate and results in undesirable isomerization of DMCD. A slight stoichiometric excess of ester or DMCD is preferred to compensate for material imbalance created during the process, thereby enhancing the polymerization rate. Preferred starting temperatures of the reaction are from about 120 to about 140 degrees Centigrade. The preferred order for adding reactants comprises charging the CHDM to the reaction vessel or container, adding the DMCD in slight stoichiometric excess, and, next, adding the catalyst to the reaction vessel containing the starting reactants at the initial reaction temperature. This step is preferably conducted under an inert atmosphere, such as nitrogen, to form a distillate which is typically collected by condensation. The distillate by-product is, based on the starting material, typically an aliphatic alcohol, such as an alkyl alcohol of 1 to 12 carbon atoms. When CHDM is reacted with DMCD, methanol is removed during the ester interchange reaction as the reaction mixture is heated from the starting temperature to about 200 to about 250, preferably from 220 to 240 degrees Centigrade.
The PCCD acid interchange oligomer formed is further reacted to form a suitable low viscosity PCCD intermediate polymer that may be solid state polymerized to form a PCCD product that is suitable for use in polymer blends. The low viscosity PCCD intermediate is formed by increasing the molecular weig
Patel Bimal Ramesh
Smith Gary Francis
Acquah Samuel A.
General Electric Company
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