Compositions – Liquid crystal compositions
Reexamination Certificate
2001-08-24
2003-12-09
Huff, Mark F. (Department: 1756)
Compositions
Liquid crystal compositions
C528S190000
Reexamination Certificate
active
06660182
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to blends of Liquid Crystal Polymers (LCPs) with thermoplastics, and more particularly to blends of stretchable liquid crystal polymers with thermoplastics suitable for use in the production of a variety of oriented shaped articles including films, fibers, and blow molded forms.
BACKGROUND OF THE INVENTION
Anisotropic melt-forming polymers, also known as liquid crystalline polymers or “LCPs” are well known in the art. LCPs exhibit a parallel ordering of molecular chains in the melt phase and are also termed “thermotropic” liquid crystal polymers. LCPs are known to have many excellent physical properties, such as higher tenacity and modulus, additionally, LCPs have good barrier resistance to many chemicals, gases and water vapor.
Blending LCPs with other thermoplastic polymers has been shown to improve some of the physical properties of the thermoplastic polymers, depending on process and rheological conditions. Furthermore, since LCPs have reduced viscosities in the melt phase, a LCP in a blend has importance as a processing flow aid for molding. Examples of blends of LCPs with thermoplastics are disclosed in U.S. Pat. Nos. 4,386,174; 4,433,083 and 4,489,190; the LCP components of such blends being polymers with highly ordered crystalline structures that, although drawable in the melt, generally lack the ability to be stretched to a significant degree at temperatures below the molten state. As used herein, liquid crystalline polymers with highly ordered crystalline structures that are not able to be stretched to a significant degree at temperatures below their molten state are referred to as “conventional LCPs”.
A problem frequently encountered with blends of conventional LCPs and thermoplastics is that the improvement of their physical properties may be hampered due to the incompatibility of the conventional LCPs with the post extrusion orientation techniques commonly utilized for many thermoplastic articles. This problem is believed to be due to poor adhesion between the conventional LCPs and the thermoplastics and the inability to stretch these LCPs at normal orientation conditions of many non-liquid crystal thermoplastics. Compatibilizers, such as those described in WO 93/24754 and WO 96/00752, have been known to improve properties of the blend, but even they are insufficient especially when the blends are used in oriented articles such as fiber or films formed by stretching because conventional LCP domains do not stretch at temperatures below their melting point. Fiber or film made from such blends and oriented at temperatures typically used to stretch non-liquid crystal thermoplastics, result in separation of the LCP from the thermoplastic matrix resulting in poorer physical properties such as break strain or toughness.
Therefore, it is an objective of the present invention to improve the physical properties of LCP/thermoplastic blends.
It is another object of the present invention to improve the physical properties of oriented articles made from LCP/thermoplastic blends.
SUMMARY OF THE INVENTION
The objects of the present invention are achieved by providing stretchable LCPs to be used in the LCP/thermoplastic blend. These stretchable LCPs can be stretched at the same temperature range as many of the non-liquid crystal thermoplastics commonly used in extrusion applications, e.g., the production of fibers, films, blow molded articles, and the like. During a post orientation process, such as fiber or film stretching, the stretchable LCP can stretch and deform along with the non-liquid crystal thermoplastic matrix, maintaining adhesion between the LCP domains and the thermoplastic matrix. It has been found that blends in accordance with the subject invention provide oriented articles, for example fibers, films and blow molded articles, having improved toughness compared to oriented articles made from blends of conventional LCPs and non-liquid crystal thermoplastics.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a melt mixture of a stretchable LCP with a thermoplastic polymer resulting in a blend with improved physical properties as compared to a conventional LCP blend. In a further embodiment, this invention relates to blends of stretchable LCPs, and thermoplastics, wherein said stretchable LCPs are present in such blends in an amount of from about 1 to about 30 percent by weight, based on the total weight of the LCP and thermoplastic components thereof.
The extent to which a polymer can be stretched or drawn depends upon the temperature at which stretching occurs as well as the form and size of the material that is being stretched. In the present application, the term “stretchable” polymer means a polymer capable of being stretched to at least 100% elongation (i.e., at least 100% break strain) before the break or rupture, when spun into tapes and tested according to the Tape Stretching Procedure set forth below. Break strain or percent elongation is the final length (L
f
) of the polymer after stretching minus the initial length (L
i
) before stretching divided by the initial length L
i
and multiplied by 100 (i.e., % elongation=[(L
f
−L
i
)/L
i
)]×100). For a film or other flat articles, the percent elongation is measured by the initial and final areas of the article (i.e., % elongation=[(final area—initial area)/initial area]×100).
Preferably, the stretchable LCPs of the present invention can be stretched to at least about 100%, 150%, 200% or even 500% elongation without tearing or breaking using the Tape Stretching Procedure set forth below.
The preferred stretchable LCPs of the present invention are, wholly aromatic LCPs. Examples of stretchable LCPs can be found in U.S. Pat. No. 5,656,714; U.S. application Ser. No.: 09/483,103, now U.S. Pat. No. 6,222,000; U.S. application Ser. No.: 09/484,120, now U.S. Pat. No. 6,132,884; U.S. application Ser. No 09/483,765, now U.S. Pat. No. 6,207,790; and copending U.S. application Ser. No. 09/783,057; all of which are herein incorporated by reference in their entirety.
Stretchable LCPs are included among LCPs comprised of recurring units I, II, III, IV and V, where recurring unit I is
recurring unit II is:
recurring unit III is:
where Ar
1
is selected from the group consisting of:
and mixtures thereof;
recurring unit IV is:
—O—Ar
2
—X— IV
where Ar
2
is selected from the group consisting of:
and mixtures thereof, and X is independently selected from the group consisting of O and NR
2
where R
2
is independently selected from the group consisting of hydrogen and a C
1
to C
6
alkyl; and
recurring unit V is a formula selected from the group consisting of:
and mixtures thereof, where R
1
is independently selected from the group consisting of hydrogen and C
1
to C
6
alkyl. To be stretchable, such polymers are required to contain specific amounts of particular recurring units. For example, stretchable LCPs having such recurring units include polymers which consist essentially of recurring units I, II, III, IV, and V wherein:
recurring unit I is
recurring unit II is:
recurring unit III is:
wherein Ar
1
is selected from the group consisting of:
and mixtures thereof;
recurring unit IV is:
—O—Ar
2
—X—
wherein Ar
2
is selected from the group consisting of:
and mixtures thereof, and X is independently selected from the group consisting of O and NR
2
wherein R
2
is independently selected from the group consisting of hydrogen and a C
1
to C
6
alkyl; and
recurring unit V is selected from the group consisting of:
and mixtures thereof, wherein R
1
is independently selected from the group consisting of hydrogen and C
1
to C
6
alkyl;
wherein recurring unit I is present in the polymer in an amount of from about 15 to about 60 mole percent, recurring unit II is present in the polymer in an amount of from about 15 to about 60 mole percent, recurring unit III is present in the polymer in an amount of from about 5 to about: 20 mole percent, recurring unit IV is present in the polymer in
Huff Mark F.
Sadula Jennifer R
Ticona LLC
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