Production of improved polymers via the use of star cores

Details Production of improved polymers via the use of star cores Production of improved polymers via the use of star cores

2001-03-21

2003-11-11

Short, Patricia A. (Department: 1712)

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

Synthetic resins

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

C560S089000, C562S887000, C562S888000, C562S895000

Reexamination Certificate

active

06646062

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a process for producing high molecular weight polymers.
The invention also relates to star cores which may be used in the production of the above polymers. More particularly, the star cores are bi-functional (“I”), tri-functional (“Y”) and tetra-functional (“H”) polymer cores.
BACKGROUND TO THE INVENTION
It will be appreciated that whilst the following specific description refers to polyester polymers and applications of these to stretch blow moulding, the invention is not so limited.
It is now the practice to produce high molecular weight polymer as a melt of intrinsic viscosity about 0.6 dl/g, then extrude and freeze the product to give pellets that are further polymerised by solid state polymerisation to give intrinsic viscosity of 0.8 dl/g for stretch blow moulding and 1.0 dl/g for high tenacity fibre for tyre cord. The pellets are melted and then formed. It is recognised that production of suitable weight average molecular weight in the original melt, followed by immediate use of the molten polymer would avoid the costly intermediate steps currently employed with further processing and has the potential to save time and energy and considerable cost.
Similarly, the desire to be able to convert polymers with a low weight average molecular weight into a polymer with a high weight average molecular weight has also been recognised as highly advantageous in, for example, fibre production.
In order for a polyethylene terephthalate (“PET”) polymer to be stretch blow moulded it must have a relatively high weight average molecular weight and sufficient intrinsic viscosity. A table linking the intrinsic viscosity with the Mw is set out in Table 1. One of the prime difficulties in producing a PET polymer polymer has been the production of a polymer with sufficient weight average molecular weight. The weight average molecular weight (Mw) of a polymer chain can be calculated as follows:
avMw=&Sgr;Mi
2
/&Sgr;Mi
where Mi is the individual polymer molecular weight.
TABLE 1
Weight Average
Molecular Weights versus Intrinsic Viscosity dl/g
IV-0.6
Mw = 33600
IV = 0.61
Mw = 34400
IV = 0.62
Mw = 35300
IV = 0.63
Mw = 36200
IV = 0.64
Mw = 37000
IV = 0.65
Mw = 37900
IV = 0.66
Mw = 38800
IV = 0.67
Mw = 39700
IV = 0.68
Mw = 40600
IV = 0.69
Mw = 41500
IV = 0.7
Mw = 42400
IV = 0.71
Mw = 43400
IV = 0.72
Mw = 44300
IV = 0.73
Mw = 45200
IV = 0.74
Mw = 46200
IV = 0.75
Mw = 47100
IV = 0.76
Mw = 48100
IV = 0.77
Mw = 49100
IV = 0.78
Mw = 50000
IV = 0.79
Mw = 51000
IV = 0.8
Mw = 52000
IV = 0.81
Mw = 53000
IV = 0.82
Mw = 54000
IV = 0.83
Mw = 55000
IV = 0.84
Mw = 56000
IV = 0.85
Mw = 57000
IV = 0.86
Mw = 58000
IV = 0.87
Mw = 59000
IV = 0.88
Mw = 60100
IV = 0.89
Mw = 61100
IV = 0.9
Mw = 62200
IV = 0.91
Mw = 63200
IV = 0.92
Mw = 64300
IV = 0.93
Mw = 65400
IV = 0.94
Mw = 66400
IV = 0.95
Mw = 67500
IV = 0.96
Mw = 68600
IV = 0.97
Mw = 69700
IV = 0.98
Mw = 70800
IV = 0.99
Mw = 71900
IV = 1.
Mw = 73000
From a theoretical perspective, in order for a PET polymer to be capable of being stretch blow moulded it must have an intrinsic viscosity in the range of 0.7 to 0.8 dl/g. The viscosity can be determined if the weight average molecular weight of the polymer chain is known since the logarithm of the melt viscosity is related to the square root of the weight average molecular weight of the polymer chain. The equation for melt viscosity is:
log(
n
)=constant*(
avMw
)
where n is viscosity and Mw is weight average molecular weight. Thus the technically important flow characteristics required during stretch blow moulding (such as injection moulding) are dependent on the weight average molecular weight.
Even where a sufficient Mw is achieved, another substantial problem in polymers has been the tendency during polymerization of the polymer to gel. During uncontrolled polymerization the random cross-linking and branching reactions that occur result in gelled products due to the highly branched structures. Such polymer structures are unsuitable for stretch blow moulding or fibre production. It has been recognised that polymers suitable for stretch blow moulding should have a small change in viscosity when the shear is changed and this property is found in linear polymers. In contrast, polymers containing polymers with many randomly spaced branches are gel-like and do not have this property.
Accordingly, investigations were conducted to develop a process to prepare polymers that have controlled degrees of branching and have a central core attaching linear chains and polymers with multifunctional centres or cores to which linear polymers preferentially attach.
It is known from the prior art that linear polymers may be altered to so-called star polymers by using small proportions of polyfunctional additives which form the “core” of the star polymer and allow linear polymers to attach thus increasing the weight average molecular weight of the resulting polymer. There is a considerable body of knowledge of these star polymers that allows the properties of a given preparation of polymer to be anticipated (for example, J. R. Schaefgen & P. J. Flory; J. Am. Chem. Soc. 70,2709,1948 “Schaefgen”). The processes in the prior art use substances that are thermally unstable, expensive and produce yellow by-products, and further these processes produce products with gel branching.
Schaefgen discloses very early research in the use of star polymers. This research explored the use of polyamines and polybasic acids (such as polyacrylic acid) however, no commercially useful products were produced. Schaefgen while describing the theoretical basis of star polymers and correctly anticipating the problems does not give any practical solutions. Moreover, Schaefgen is not directed to the formation of PET polymers which have unique problems because being ester polymers, it is difficult to develop appropriate polyfunctional compounds.
The use of polyfunctional cores is also disclosed in U.S. Pat. Nos. 3,692,744, 3,714,125 and 3,673,139.
In U.S. Pat. No. 3,673,139, the increased viscosity and gummy elasticity of polyesters due to the increasing degrees of cross-linking or branching was recognised and sought to be addressed by condensing during the processing of the polymer, 0.001 to 1 mol % of a compound having not less than three polyester forming functional groups so as to form slightly branched or cross-linked polyesters with an intrinsic viscosity of at least 0.8 dl/g or preferably 0.9 dl/g and a substance which promotes crystallisation. The process disclosed is a reaction of terephthalic acid ester, ethylene glycol and the polyester forming group. The products of this process are unsatisfactory as they do not meet the required colour and linear viscosity characteristic with the low addition rate described.
U.S. Pat. No. 3,692,744 discloses the inclusion in a poly-esterification mixture, in addition to a terephthalic acid component and a diol component, of 0.05-3 moles percent of the acid component of a compound containing at least 3, preferably 3-4, ester forming groups (for example, a tri- or tetra-carboxylic acid, a triol or tetrol or a hydroxy carboxylic acid containing in all 3 or more ester-forming groups). Again, the methods disclosed in this art provide for the addition of the polyfunctional compound as a starting material. This patent discloses the use of triols and tetraols that are unsuitable because the substances are unstable and at temperatures higher than about 290° C. dehydrate to give a double carbon bond which produce

Affiliated with

Also associated with

Rating

Production of improved polymers via the use of star cores does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Production of improved polymers via the use of star cores, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Production of improved polymers via the use of star cores will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3158793