KR20010013007A - Films made from long chain branched syndiotactic vinyl aromatic polymers - Google Patents

Abstract

The present invention is directed to films prepared from a composition comprising a long chain branched syndiotactic vinyl aromatic polymer. Long chain branches can be produced during polymerization by polymerizing in the presence of a small amount of a difunctional monomer.

Description

FILMS MADE FROM LONG CHAIN BRANCHED SYNDIOTACTIC VINYL AROMATIC POLYMERS} Films made from long chain branched syndiotactic vinyl aromatic polymers

Syndiotactic copolymers have also been developed to have excellent heat and chemical resistance. U.S. Pat.No. 5,202,402 to Funaki et al. Uses bifunctional monomers to form syndiotactic copolymers with styrene, although the polymers are fully crosslinked at high temperatures to form thermosets, Melt processing does not produce a film, but instead uses a melt casting process which is slow and has the added problem of solvent removal.

Films have been made from linear syndiotactic vinyl aromatic polymers as described in US Pat. No. 5,166,238, US Pat. No. 5,093,758 and US Pat. No. 5,188,930. However, films made from linear syndiotactic vinyl aromatic polymers are known to have poor tear strength in manufacturing and application.

Thus, it would be useful to obtain a syndiotactic vinyl aromatic polymer having good heat resistance and chemical resistance that can be melt processed at high temperature while maintaining good melt strength so that a film with good tear strength can be obtained.

The present invention relates to syndiotactic vinyl aromatic polymers and films made therefrom.

Syndiotactic vinyl aromatic polymers such as syndiotactic polystyrene (SPS) are useful polymers with high melting point and crystallization rate as well as excellent heat and chemical resistance. However, in some applications, such as in cast-tenter films and fibers, the melt strength is insufficient to obtain the desired properties at processing temperatures.

The present invention relates to a film made from a composition comprising a long chain branched syndiotactic vinyl aromatic polymer. Long chain branches can be prepared during polymerization by polymerizing in the presence of small amounts of bifunctional monomers. Films of the invention have improved melt strength and tear strength.

In one aspect, the invention relates to a film made from a composition comprising a long chain branched syndiotactic vinyl aromatic (LCB-SVA) polymer.

As used herein, the term "syndiotactic" refers to syndiotactic stereoregular structures of at least 90%, preferably at least 95%, of racemic triads as measured by a 13C nuclear magnetic resonance spectrometer. Refers to a polymer having

Syndiotactic vinyl aromatic polymers are homopolymers and copolymers of vinyl aromatic monomers, ie monomers whose chemical structure has both unsaturated and aromatic residues. Preferred vinyl aromatic monomers have the formula H ₂ C═CR-Ar, wherein R is hydrogen or an alkyl group having 1 to 4 carbon atoms and Ar is an aromatic radical having 6 to 10 carbon atoms. Examples of such vinyl aromatic monomers include styrene, α-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl toluene, para-tert-butylstyrene and vinyl naphthalene; Bromo-substituted styrenes, in particular p-vinyltoluene and ring brominated or ibrominated styrenes. Brominated styrene is particularly useful for preparing fire resistant syndiotactic vinyl aromatic polymers. Alternatively, a fire resistant LCB-SVA polymer can be prepared by brominating the LCB-SVA polymer. Representative syndiotactic copolymers include styrene-p-methylstyrene, styrene-p-tert-butylstyrene and styrene-vinyl toluene copolymers. Syndiotactic vinyl aromatic polymers and monomers prepared therefrom are described, for example, in US-A-4,680,353, US-A-4,959,435, US-A-4,950,724 and US-A-4,774,301, incorporated herein by reference. It is already disclosed in the literature. Syndiotactic polystyrene is a presently preferred syndiotactic vinyl aromatic polymer.

Long chain branching can be achieved by polymerizing vinyl aromatic monomers in the presence of small amounts of multifunctional monomers under conditions sufficient to produce syndiotactic vinyl aromatic polymers. Multifunctional monomers are any compounds having one or more olefinic functional groups capable of reacting with vinyl aromatic monomers under polymerization conditions. Typically, the multifunctional monomer will contain 2 to 4 olefinic functional groups, which are represented by the formula:

Where

R is from 2 to 20 comprising terminal vinyl groups, which may be vinyl groups or alkyl, alkenyl, cycloalkyl groups (which contain at least 5 carbon atoms) or aromatic groups (which contain at least 6 carbon atoms) Group containing two carbon atoms,

n is an integer from 1 to 3, wherein

The R group is meta or para position relative to the vinyl group of formula (I) and may be the same or different when n is greater than 1.

It is preferred that R is a vinyl group.

Preferably, the multifunctional monomer comprises two terminal vinyl groups, where n is one. Typically such monomers include difunctional vinyl aromatic monomers such as di-vinyl-benzene or di-styryl-ethane.

The amount of polyfunctional monomer depends on the weight average molecular weight (M _w ) of the polymer to be produced, but is typically at least 10 ppm, preferably at least 50 ppm, more preferably at least 75 ppm and most preferred based on the amount of vinyl aromatic monomer. Preferably from 100 ppm to 1000 ppm, preferably 800 ppm or less, more preferably 500 ppm or less and most preferably 650 ppm or less.

The multifunctional monomer can be induced into the polymerization by any method that allows it to react with the vinyl aromatic monomer during the polymerization to produce the LCB-SVA polymer. For example, the multifunctional monomer may be first dissolved in the vinyl aromatic monomer prior to the polymerization, or may be individually introduced into the polymerization reactor before or during the polymerization. In addition, the multifunctional monomers can be dissolved in the inert solvent used in the polymerization, such as toluene or ethyl benzene.

Any polymerization method for preparing syndiotactic vinyl aromatic polymers can be used to prepare the LCB-SVA polymers of the present invention as long as the multifunctional monomer is further present during the polymerization. Typical polymerization processes for making syndiotactic vinyl aromatic polymers are well known in the art and described in US-A-4,680,353, US-A-5,066,741, US-A-5,206,197 and US-A-5,294,685. It is. Typically, the weight average molecular weight (M _w ) of the LCB-SVA polymer is at least 50,000, preferably at least 100,000, more preferably at least 125,000 and most preferably at 150,000 to 3,000,000, preferably at most 1,000,000, more preferably 500,000 or less and most preferably 350,000 or less.

Branched syndiotactic vinyl aromatic polymers include extensions of the syndiotactic vinyl aromatic polymer chains attached to the polymer backbone. Long chain branched syndiotactic vinyl aromatic polymers typically comprise chain extensions of at least 10, preferably at least 100, more preferably at least 300 and most preferably at least 500 monomer repeat units.

Typically, the films of the present invention are made from compositions of LCB-SVA polymers in the absence of other polymers. However, films can be made from compositions comprising LCB-SVA polymers and other components including other polymers. The amount of LCB-SVA polymer contained in the composition for making the film depends on the end use, in which case only small amounts can be used to benefit. Generally, at least 5%, typically at least 20%, preferably at least 40%, more preferably at least 70% and most preferably 100% by weight of the LCB-SVA polymer is used in the composition for making the film. do. Other polymers that may be included in such compositions include linear SPS, polystyrene, polyphenylene oxide, polyolefins such as polypropylene, polyethylene, poly (4-methylpentene), ethylene-propylene copolymers, ethylene-butene-propylene copolymers , Nylons such as nylon-6, nylon-6,6; Polyesters such as poly (ethylene terephthalate), poly (butylene terephthalate), and copolymers thereof or blends thereof Antioxidants, and alumina, silica, aluminosilicates, carbonic acid Other materials or additives including anti-sticking agents such as fine particles of calcium, calcium phosphate and silicon resins; Coupling agents (e.g., maleated polymers), and binders to improve the wet strength of the base fabric, brominated polystyrene, brominated syndiotactic vinyl aromatic polymers, antimony trioxide, and LCB-SVA polymers Films or articles were made from polytetrafluoroethylene that could be added to the composition.

The film of the present invention can be obtained as a single layer film or a multilayer film structure. Typically, the films of the present invention are about 1 micron to 10 mils thick, but can also be obtained with a thickness of 50 mils or less. In addition, a film sheet can be obtained that can have a thickness of 125 mils or less.

Films of the present invention can be made by a variety of processes, including the steps of blowing and casting / tentering the film. Typically, the LCB-SVA polymer is heated in a melt extruder and delivered to a vertical die, and the molten polymer is deposited in the form of a continuous sheet or web on a large cylinder or casting drum, as is well known in the art. Similarly oriented and stretched casting / tentering processes are used.

Films of the invention can also be coated or laminated with other films or coatings to add additional properties to the film.

Films of the invention can be used in optical magnetic media, electrical appliances, packaging products, release films, automotive and architectural applications.

The following examples are provided to illustrate the invention. The examples are not intended to limit the scope of the invention and should not be so interpreted. Unless otherwise indicated, amounts are expressed in parts by weight or weight percent.

Example 1

How to prepare LCB-SPS

All reactions are carried out in an inert atmosphere in a dry box. Reagents, toluene and styrene monomers are purified and manipulated using standard inert atmosphere techniques. Di-styryl-ethane is prepared according to the procedure described in W.H. Li et al., J. Polymer Sci., Part A, Polymer Chem., 32 (1994) 2023.

Polymerize in a 5 "Teledyne kneader-mixer as described in US-A-5,254,647. A solution of 1.3% by weight of di-styryl-ethane in toluene is added to the styrene monomer in the amounts listed in Table 1. Added and fed to the reactor at 17.5 kg / hour to give an average residence time for 18 minutes polymerized at 55 to 67.5 ° C. Octahydrofluorenyl titanium with the required amounts of methylalumoxane and triisobutylaluminum Trimethoxy catalyst (0.007M) is fed to the reactor in a molar ratio of styrene to titanium of 80,000: 1 to 100,000: 1 The product is a fine white powder with a conversion rate of 36 to 50% The sample is collected under nitrogen and excess The sample is then quenched by addition of methanol in. The sample is then dried in a nitrogen-sintered 5 mm Hg vacuum oven for 2 hours The weight average molecular weight (M _w ) of the polymer is determined by hot size exclusion chromatography. The results are shown in Table 1:

Sample ppm DSE M _w M _n M _z M _w / M _n One 400 294,900 82,100 1,151,900 3.59 2 400 334,800 86,500 1,377,300 3.87 3 250 420,000 92,300 2,418,300 4.55 4 250 368,900 71,600 1,962,000 5.15

Significant increase in M _z by di-styryl-ethane indicates long chain branching. The sample in powder form is converted into pellets using a 0.5 "uni-screw compressor. The molecular weight of the pellets is summarized below:

Sample M _w M _n M _z M _w / M _n One 279,900 75,000 1,137,400 3.73 2 304,900 82,000 1,161,100 3.72 3 313,000 74,900 1,294,900 4.18 4 301,000 65,000 1,204,900 4.63

As described in SK Goyal's "Plastics Engineering, 51, (2), 25, 1995" using a plunger speed of 1 in / min, winder speed of 50 ft / min, and test conditions of 279 ° C. The melt strength is measured according to the technique. Melt flow rate is measured according to ASTM method D1238 using a load of 1.2 Kg and a test condition of 300 ° C. 300,000 M _w of linear SPS polymer is used as a control. The results are summarized below:

Sample Melt strength (g) MFR (g / 10 min) One 4.0 19.1 2 5.4 14.4 3 5.5 15.5 4 4.5 17.1 Control 1.9 3.6

LCB-SPS samples have higher melt strength and melt flow rate than linear SPS control samples.

Example 2

LCB-SPS and Process for Making Film Sheets Therefrom

The polymerization is carried out in a 5 "teredane kneader for an average residence time of 18 minutes and then in a 500 L tank reactor for an average residence time of 10 hours. The operation of these devices is described in US-A-5,254,647. Styrene monomers are mixed with 250 ppm of a 3.3% solution of di-styryl-ethane in toluene and fed to the reactor at 17.5 kg / hr, polymerized at 55 ° C. Methylaluminoxane, triisobutylaluminum and octa The catalyst solution of hydrofluorenyltitanium trimethoxide is also fed to the reactor in a molar ratio of styrene to titanium of 80,000: 1 After polymerization, the polymer is devolatilized and pelletized as described above. Measured via size exclusion chromatography and the results are shown below:

M _w M _n M _z M _z +1 M _w / M _n 284,000 61,400 1,049,500 2,178,900 4.63

300,000 M _w of linear SPS polymer is used as a control.

LCB-SPS and linear SPS polymers are converted to film sheets using the following process: Resin pellets are fed into a 1 in Killion single-screw extruder at 300 ° C., extruded through a slit die, and main at 88 ° C. Quenching in a modeling drum produces a sheet of 10 mil thickness (250μ). Sheets were simultaneously placed in two axial directions under stretching conditions (ie stretching temperature of 110 ° C., sample preheating time of 2 minutes, stretching rate of 1200% / min and elongation of 3.5) in an Iwamoto BIX-703 drawing machine. Stretching produces 1 mil (25 μ) of film. 20% of the linear SPS film is broken during the film drawing process, but no LCB-SPS film is broken under the same drawing conditions. The prepared film is annealed with the film edge adhered onto the metal mold in an oven at 220 ° C. for 1 minute.

The tear strength of the film is measured according to ASTM D1938. The average tear strength of the LCB-SPS film is 2.67 g / mil, which is 44% higher than the 1.86 g / mil of the linear SPS film.

Claims (6)

A film made from a composition comprising a long chain branched syndiotactic vinyl aromatic polymer. The method of claim 1, A film wherein the vinyl aromatic polymer is polystyrene. The method of claim 1, A film wherein the vinyl aromatic polymer is a copolymer of styrene and para-methylstyrene. The method of claim 1, Film with a thickness of 1μ to 50mil. The method of claim 1, Film in the form of a sheet. The method of claim 5, Film sheet having a thickness of 50 mils to 125 mils.