NO772003L - FILM-MIXING MIXTURE. - Google Patents

Description

The present invention relates to a rollable (calenderable) film-forming mixture which, after calendering, is suitable for use as a vapor barrier. The film made in this way has low . water vapor permeability, low heat dissipation and smoke formation properties, and low brittleness temperature.

Previously known vapor barrier compositions, which are suitable

for use in the manufacture of insulation for buildings and as a wrapping material for air duct and pipe insulation which is made using polyvinyl chloride as the main component, exhibits good flame spread and smoke formation properties, but usually has poor water vapor permeability properties and a marginal brittleness temperature or cold cracking resistance. The water vapor permeability of such a product is the most important of these physical properties and usually varies between 1.0 and 1.3 "English perms" when measured according to ASTM E 96-66-70, Method A. To achieve a more desirable performance , e.g. about. 0.1-0.3 "English perms", it was necessary to use more expensive cladding products which include either vinyl laminates or aluminum foil.

The present invention is a calenderable film-forming mixture comprising polyvinyl chloride, mainly amorphous, chlorinated polyethylene and an epoxy plasticizer. When the mixture is calendered into a self-supporting film, it has a greatly reduced water vapor permeability and improved cold break and smoke formation properties compared to conventional vinyl chloride polymer films, while retaining the good flame spread of prior art films.

The main component in the calenderable, film-forming composition according to the invention is a polyvinyl chloride polymer which can be calendered. Such resins are well known to those skilled in the art. These polymers are low and medium molecular weight polyvinyl chloride polymers with a relative viscosity of from about 1.75 to about 2.50 when measured as a 1% solution in cyclohexanone at 25°C. Particularly preferred are homopolymers of vinyl chloride with a relative viscosity of approx. 2.00 to approx. 2.45, and with values of approx. 2.20 more. about.

2.30 as particularly preferred because they are easy to handle. Suitable resins of this type are commercially available from Stauffer Chemical Company, Plastics Division. Resins with the designations "SCC-608" through "SCC-676" are suitable for use in the present invention. Calenderable vinyl chloride copolymers are also useful. When the selected comonomers have good flame retardant properties, such as e.g. vinylidene chloride, relatively larger quantities can be used than comonomers with a greater flammability, such as e.g. vinyl acetate. A representative list of suitable vinyl chloride copolymers can be found in US application 502,590, filed September 3, 1974, which is hereby incorporated by reference. These homo- and copolymers give the calendered film product the tensile strength, abrasion resistance and elongation properties desired by the person skilled in the art. Rapid melting and mixing of the various ingredients used in the production of the film is made easier by using such polymers. The amount of polyvinyl chloride in the film-forming mixture can vary from approx. 30 to approx. 40, preferably from approx. 35 to approx. 38% by weight.

As an aid in softening the polyvinyl chloride (PVC), as well as to contribute to improved water vapor permeability, flame hxcling and cold fracture resistance, in the present invention an essentially amorphous, chlorinated polyethylene polymer with a chlorine content of from approx. 3 5 to approx. 50%. This polymer, in order to be useful in forming a calenderable, film-forming mixture, has a low melt viscosity value for it to be calenderable. Preferred chlorinated polyethylene polymers have a crystal content of from essentially zero to a maximum of about 0.2%

(measured using differential heat analysis) and a melt viscosity of from approx. 8,000 to approx. 20,000 poise measured on an "Instron Rheometer" at 190°C and 150 sec. The term "substantially amorphous", as used herein, shall be understood to include the foregoing sets of values. These polymers also exhibit a high modulus of elasticity, namely approx. 275 to approx. 350% measured as a 100% chlorinated polyethylene film. Such chlorinated polyethylene polymers are commercially available, for example from The Dow Chemical Company. The amount of chlorinated polyethylene used in the present film-forming composition should vary between approx. 35 and approx. 45% by weight of the mixture, preferably from approx. 30 to approx. 40% by weight.

If the relative amounts of polyvinyl chloride and chlorinated polyethylene (CPE) are expressed by weight ratio between them, the relative amounts can vary from approx. 0.80:1.00 to approx. 0.95:1.00 between the former and the latter, preferably from approx. 0.85:1.00 to approx. 0.92:1.00, to give the calendered film formed from the film-forming mixture the degree of stiffness or "hand" required by people in the construction industry.

To aid in the softening of the PVC/CPE blend described above, without causing an increase in either the water vapor permeability of a calendered film formed from the ceram or in the heat sensitivity of the blend, an effective amount of an epoxy plasticizer is added to effect this. The amount used is usually from approx. 2 to approx. 8% by weight of the mixture, preferably from approx. 4 to approx. 6% by weight. Epoxy plasticizers with an oxirane content of from approx. 5 to approx. 8% by weight gives the desired degree of thermal stability

to the mixture. Some examples of suitable epoxy plasticizers are suitable epoxy plasticizers with the above properties, as well as epoxidized dctyl thallate, epoxidized soybean oil, epoxidized triglyceride, epoxidized linseed oil and 2-ethylhexyl epoxytallate.

In order to increase the flame retardancy of the film, if desired, conventional, compatible flame retardants can be added to the film-forming mixture. The amount added will usually go up to a maximum of approx. 6% by weight of the composition, preferably from approx. 1 to approx. 5% by weight. Some examples of suitable flame retardant additives are finely divided antimony trioxide (available from M&T Chemicals Co. as eg "ThermoguardB") and hydrated alumina.

To ensure the heat stability of the final product if commercial calendering operations are to be used, the mixture contains from 3-7% by weight of conventional heat stabilizers. The conventional barium/cadmium stabilizers, either with or without zinc, can be used. A combination of liquid and solid stabilizers is usually used in high speed calendering operations.

During most commercial calendering operations, lubrication is required to ensure roll transfer and roll release to give the film the desired surface finish. Since chlorinated polyethylene can give an increased tendency for the film to stick to adjacent film layers when it is rolled up on a roller (called "blocking"), a non-blocking agent is often mixed into the lubricant. It has been found that a combination of internal and external lubrication as well as a non-blocking agent can be used to ensure the best results. The total amount of such additives in the mixture can vary from about 0.4 to 0.7% by weight of the mixture. Preferred lubricants are stearic acid and calcium stearate, and a preferred non-blocking additive is partially oxidized polyethylene. Other compatible lubricants and non-blocking agents known to those skilled in the art, e.g. low density polyethylene can also be used.

The mixture may also contain other optional additives, e.g. antioxidants (eg bisphenol A), pigments (eg TiO^)/fillers (eg talc or kaolin clay) and desiccants (fused silica) to impart particularly desirable properties to the finished film.

The film-forming mixture according to the invention is made with

mixing the polyvinyl chloride and the fillers, pigments and flame retardants (if any) in a conventional mixer until a homogeneous mixture is obtained. The liquid ingredients, e.g. stabilizers and the epoxy plasticizer, are mixed in another mixer and then added to the first mixture. The solid stabilizer, the lubricant and chlorinated polyethylene are then added and the mixing is continued until a homogeneous mixture is formed.

The resulting mixture is then processed in an apparatus that can melt it and thereby produce a very smooth mixture. Suitable equipment for this purpose includes "intermix", sold by Adamson United, Division of Wean, Inc. (Pittsburgh, Pa.), and "Kokneader", sold by Baker Perkins Inc. (Saginaw, Mich.). It is important that this operation should also serve to remove as many volatile components from the mixture as possible. The presence of an excessive concentration of volatiles will have a detrimental influence on the flame spread and smoke density properties of films obtained from these mixtures. More particularly, it is preferred that the concentration of volatile substances in these film-forming mixtures should not be greater than approx. 2.0% by weight, when the mixture is tested for 3 hours in an oven with air circulation at 104°C.

After the melting operation, the resulting mixture can be stored or immediately passed through a calender or other suitable apparatus which can convert the mixture into a thin, self-supporting film. The resulting films can have a thickness in the range from approx. 0.051 - 1.524 mm, and with a thickness of approx. 0.076 - 0.102 mm as optimum for most purposes. Those skilled in the art will naturally understand that . the method of manufacture described above is only illustrative and

can be varied in an appropriate manner if desired.

The films obtained from the new film-forming mixture according to the invention exhibit good water vapor permeability resistance, low flame spread and smoke formation properties and good low temperature embrittlement properties. They are therefore particularly well suited for use in a number of building constructions where the materials used must exhibit such properties. These films can thus be used for the production of vapor barrier constructions by being laminated to part of the insulation material, such as e.g. fiberglass pieces with a thickness of from approx.0.64 to 7.6. cm with a suitable fire-retardant adhesive such as e.g. the water-based adhesives containing one or more vinyl homo- or copolymers dissolved or emulsified therein.

The following examples will illustrate the different embodiments of the invention. In these examples, all parts are stated as parts by weight unless otherwise stated.

Examples 1-5

These examples illustrate the preparation of compositions according to the invention (Examples 1 and 2) and three other known compositions (Examples 3-5) together with data for their permeability, flame spread, smoke generation, cold fracture and stiffness.

All mixtures were prepared using the following general procedure: Polyvinyl chloride resin, fillers, pigments and flame retardants used for the production of the respective films were placed in a 22 70 kg ribbon mixer which was not heated during mixing, if chlorinated was to be added polyethylene during the production of the film. The mixture was carried out for approx.

15 minutes until a homogeneous mixture was obtained. In a separate container, the liquid ingredients, e.g. the liquid stabilizer and the liquid epomixer placed. After these were mixed, they were added to the ribbon mixer. Mixing of the solid and liquid components was continued for approx. lo minutes, at which point the solid stabilizer, the lubricants and the chlorinated polyethylene (if used) were added. Mixing was continued for a further 15 minutes. The dry mixture was then placed on a conveyor belt and taken to a melter where it was kneaded under the application of heat and pressure into a plastic mass. This mass was then calendered at a temperature of approx. 170°C, for the film with polyvinyl chloride as the only resin, and at a temperature of approx. 135°C, for the films which also contained chlorinated polyethylene. The film had a thickness of 0.076 - 0.102 mm after calendering.

The table listed below gives the compositions of the batches for a film formed according to the present invention (Examples 1 and 2) and three other films (Examples 3-5) which are not part of the present invention.

Footnotes:

la) Available as "XP 2243.46" from The Dow Chemical company.

It contains approx. 42% chlorine, essentially 0% crystallinity and has a melt viscosity of approx. 9,500 poise, determined with an "Instron Rheometer" at 19o°C and 150 sec-1.

lb) Available as "XP 2243.30" from TheDow Chemical Company.

It contains approx. 30% chlorine, 17% crystallinity and has a melt viscosity of approx. 27,000 poise, determined with an "Instron

. Rheometer" at 190°C and 150 sec-1.

lc) Available as "XO 2243.49" from The Dow Chemical Company.

It contains approx. 42% chlorine, essentially 0% crystallinity and has a melt viscosity of approx. 19,500 poise, determined with an "InstronRheometer" at 190°C and 150 sec-"1'.

2) Available as "SCC-616" (No. 1 and 3-5) and "SCC-614"

(No. 2) from Stauffer Chemical Company. SCC-614 is a low molecular weight PVC homopolymer with a relative viscosity of approx. 1.97 as a 1%-µg solution in cyclohexanone at 25°C.

SCC-616 is an intermediate molecular weight PVC homopolymer with a relative viscosity of 2.08. 3) Available as "Monoplex S-75" from Rohm and Haas Co. It has a high oxirane value of approx. 7. 4) Decyldiphenyl phosphate, available as "Santicizer 148" from Monsanto Co. 5) Available as "Thermoguard B" from M&T Chemicals Co. It has a mean particle size of less than approx. 5 microns and contains a major part of the cubic, crystallographic forms of antimony trioxide. 6) Available as "S/G 84" from The Burns and Russel Company. It is more fully described in British Patent 1,080,468. 7) Available either as "Mark Q-180" (#1) from Argus Chemical Corp. or as "Synpron 1403" (No. 2) from Synthetic Products Co., Div. of Dart Industries, Inc. 8) Available either as "Ferro 1827" (No. 1) from FerroChemical, Div. of Ferro Corp. or as "SynpronJ40" (No. 2) from Synthetic. Products Co., Div. of Dart Industries, Inc.

The former is a barium-cadmium-zinc solid.

9) Available as "Nuostable V 1541" from Tenneco Chemicals Co. 10) Available as "Nuostable V 1542" from Tenneco Chemicals Co.

11) Available as "Allide 629A" from Allied Chemical Co.

12) Talc or kaolin clay.

13) Available as "Cab-O-Sil", grade EH-5, from Cabot Corporation. 14)Indicated in English perm units or 1 gram of water vapor/24 hours/645.2 cm 2 mm Hg. It indicates the ratio between the water permeability through the sample and the vapor pressure on both sides of the sample. A low value is desirable. 15 and 16) This test determines the burning properties of the material being tested compared to corresponding properties for an asbestos-cement board (given the value 0) and a selected type of red oak for flooring (given the value 100). Low values for each characteristic are desirable. 17) Indicates the brittleness temperature for plastic films on impact. It is the temperature that has been statistically calculated at which 50% of the samples are likely to break 95% of the time a set minimum number is tested according to the method. A low temperature is desirable. 18) Measured on a "Gurly Stiffness Tester" manufactured by Teledyne Gurly, 514 Fulton Street, Troy, N.Y. 12181. This instrument measures the flexibility of sheet materials. It consists of a balanced pendulum or arrow which swings about the center and which can be weighted with different weights below its centre. The arrow moves parallel to a "sine curve", which is graded in both directions. In the test, the arrow is deflected by a material sample that is pressed against its upper end. The sample, cut to a standard length from 2.5 to 10 cm, and standard width from 1.25 to 5 cm, overlaps the top of the arrow by 0.65 cm. The sample, which is bent by the weight of the arrow, releases it. The release point is taken as a test reading.

High numbers indicate a less flexible film.

The preceding examples no. 1 and 2 shall only illustrate certain preferred embodiments of the invention and shall not be taken as any limitation. The scope of protection of the invention, as desired, is specified in the subsequent claims.

Claims (10)

1. A rollable film-forming composition suitable for use as a vapor barrier, characterized in that it comprises: a) a vinyl chloride polymer; b) an essentially amorphous chlorinated polyethylene with a chlorine content of approx. 35% to about 50% by weight; and c) an epoxy plasticizer. 2. Mixture as stated in claim 1, characterized in that the vinyl chloride polymer is present in from approx. 30 to approx. 40% by weight, calculated on the mixture. • 3. Mixture as stated in claim 1, characterized in that the vinyl chloride polymer has a relative viscosity of from approx. 1.75 to approx. 2.50, measured as a 1% by weight solution in cyclohexanone at 25°C. 4. Mixture as stated in claim 1, characterized in that the vinyl chloride polymer is a homopolymer of viriyl chloride. 5. Mixture as stated in claim 1, characterized in that the chlorinated polyethylene is present in from approx. 35 to approx. 45% by weight of the mixture. 6. Mixture as specified in claim 1, characterized in that the amount of plasticizer is from approx. 2 to approx. 8% by weight of the mixture. 7. Mixture as stated in claim 1, characterized in that the plasticizer has an oxirane content of approx. 5 to approx. 8%. 8. Mixture as specified in claim 1, characterized in that it comprises from approx. 30 to approx. 40% by weight vinyl chloride polymer, from approx. 35 to approx. 45% by weight chlorinated polyethylene and from approx. 2 to approx. 8% by weight plasticizer. 9. Mixture as stated in claim 8, characterized in that the vinyl chloride polymer is a homopolymer of vinyl chloride with a relative viscosity of from approx. 1.75 to approx. 2.25,' measured as a 1% by weight solution in cyclohexanone. 10. Mixture as stated in claim 8, characterized in that the plasticizer has an oxirane content of approx. 5 to approx. 8%.