GB1590242A - Latex blend binder compositions for asbestos sheets - Google Patents

Description

Referring to the drawing, a controllable DC (direct current) voltage supply 1 is fed with a constant DC aoltage U=. A series regulator 2 comprises a controlled rectifier 3 functioning as a chopper for which the control signals are supplied by a control device 4 in such a way that DC pulses of different width and/or frequency are allowed to pass. A downstream smoothing circuit comprises a series-connected choke 5 and a parallel-connected capacitor 6. Consequently a controllable DC voltage Ul is produced.

This voltage U1 is normally brought to a desired value which is set at the control device 4 by a setting device 7. If, however, the current in the system reaches a predetermined limiting value, which can be detected by the voltage drop across a measuring resistor 8, the control device 4 reduces the voltage Ul so that no excessively high currents can occur. Also controlled by the voltage U1 there is a frequency generator 9 which delivers a series of pulses t having a frequency six times as large as the frequency appropriate to supply to the motor for the currently-obtaining value of the voltage Ul.

This frequency generator 9 is in the form of a voltage-controlled oscillator (VCO) of known type.

An inverter 13 is connected by way of a short-circuit opposing impedance 10 which is inductive and also serves to recover energy during current-extinction with the aid of a transformer widing 11 and a rectifier 12. The inverter 13 feeds a three phase asynchronous motor 14. The inverter comprises three parallel branches a, b and c which each comprise two series-connected switch elements 15a and 16a, 15b and 16b, and 15c and 16e respectively. Each of three phase connections U, V and W to the motor is taken from the junction of the switch elements in a respective one of the branches.

The control electrodes of the switch elements (which are controlled rectifiers) are fed with high frequency ignition pulses z by way of control lines 17. For the sake of simplicity, some of the components normally provided in an inverter such as ordinary diodes not shown.

A current-extinction circuit comprises a capacitor 18, an inductor 19 to produce a reverse polarity pulse, a current-extinction switch element 20 in the form of a controlled rectifier and a diode 21. The control electrode of the switch element 20 is fed by way of a control line 22 from a current-extinction pulse generator 23 with extinction pulses 1 which are each initiated by a respective pulse of the pulse series t and thus have a frequency corresponding to six times the desired frequency to be supplied to the motor.

The pulses t also control a current-initiation signal generator 24 which can be of any desired construction and comprise for example flip-flops, frequency dividers, counting circuits etc. Current-initiations signals u, v and w corresponding to the desired phase voltages at the outputs U, V, and W are produced at the outputs of current-initiation signal generator. The signal w is passed on directly but the signals u and v are fed by way of a reversing circuit 30. They are then passed, partly directly and partly by way of respective NOT elements 32a, 32b or 32c, to lines 31a to c and 33a to c to deliver the current initiation pulses to the lines 17.

For example, they can be combined with a permanently transmitted high-frequency signal, for example 200 KHz. This high frequency signal therefore always occurs in any one of the lines 17 whenever an input signal derived from one of the signals u, v and w is also present in an associated one of the lines 31a to c and 33a to c.

The reversing circuit 30 comprises two first NAND elements 37, 38 and 39, 40 as well as a second NAND element 41 and 42 for each of the two phases to be interchanged.

There is also a latching device 43 in the form of a D-type flip flop of which the D input is selectively applied by way of a switch 44 to earth or to the voltage of a voltage source 45 so that the D input is fed with a phase reversal signal p having the value 1 for one direction of rotation and the value 0 for the other direction. Each of the two values is associated with a respective one of two reversing signals namely sl at the Q output and s2 at the Q output. However, a reversal at the outputs takes place only on the occurence of a pulse t at the clock input C1. This means that the phase reversal signal p can be given at a desired instant but a change of the reversal signals sl and s2 is effected only on the occurrence of a pulse t which simulataneously brings about currentextinction by way of the current-extinction signal generator 23.Depending on these reversing signals sl and s2, either the NAND elements 37 and 39 or the NAND elements 38 and 40 become effective so that the branch a is selectively controlled by the currentinitiation signal u or v and the branch b selectively by the current-initiation signal v or u, this provides the ability to reverse the direction of rotation of the motor.

Assuming that the reversing signal sl is present, the circuit then operates so that the phase voltages occur in the sequence U, V and W. If the switch 44 is operated, a change in the reversing signal to s2 will take place when the next pulse t occurs. The phase voltages will now be controlled in the order V, U, W, which corresponds to a reversal of the rotary field in the motor 14.

Since the reversal takes place at the instant of current-extinction, no short circuit need be feared in the branches a, b and c. Immedi ately after this reversal, the motor will act as a generator and is therefore braked.

Because of the currents that arise, the voltages U1 is reduced, whereby the frequency of the frequency generator 9 will also drop. As soon as the motor 14 has come to rest, it will immediately accelerate in the opposite sense, the voltage U1 and the frequency then increasing up to the desired value.

Numerous modifications are possible. For example, the latching device may also be initiated by a current-extinction pulse. The NAND elements may also be replaced by AND elements, and vice versa, if the circuit is adapted accordingly.

WHAT WE CLAIM IS 1. A control circuit for a polyphase electric motor comprising a polyphase inverter including a network of current switching elements operable in sequence to produce a polyphase supply for said motor, current-extinguishing means operative to stop current flow through each element at the end of the particular element's turn in the sequence, and a reversing circuit operative to change the control sequence of the switching elements to reverse the phase order at the output of the inverter to effect motor reversal, wherein the reversing circuit is arranged to change the control sequence only at times when the current extinguishing means is, or is just about to be, operative.

2. A control circuit as claimed in claim 1, wherein a source of controlled DC (direct current) input voltage is provided for the inverter, means are provided to control the output frequency of the inverter in proportion to the magnitude of the DC input voltage, and means are provided to decrease the DC input voltage if the current taken by the inverter reaches a predetermined limit.

3. A control circuit for controlling the speed and rotary direction of a three-phase asynchronous motor energised by a controllable DC supply by way of a short-circuit opposing impedance and an inverter, the controllable DC voltage being arranged to be lowered on reaching a limiting current, comprising a frequency generator for determining the speed, a current-initiation signal generator arranged to be influenced thereby and connected by control lines to inverter switch elements which are arranged in series in pairs in at least three branches, and an current-extinction signal generator also atranged to be influenced thereby for controlling a common current-extinguishing switch element, and a reversing circuit, to influence the rotary direction, for exchanging the control lines of the inverter switch elements of at least two branches, wherein the reversing circuit is associated with a latching device which prevents an initiated reversal from taking effect until the instant of the next following current-extinction, and the frequency of the frequency generator is arranged to be proportional to the controlled DC voltage.

4. A control circuit as claimed in claim 3, wherein the frequency generator is arranged to deliver a pulse for releasing the latching device at each instant of current-extinction.

5. A control circuit as claimed in claim 3 or claim 4, wherein the latching device is arranged to deliver one of two alternatively occurring reversing signals in response to a supplied phase reversal signal but permits a signal change only on the next following current-extinction, and wherein the reversing circuit has in each branch to be reversed two electronic switch elements in which the current-initiation signals of each phase of the current-initiation signal generator are interlinked after an AND function with a respective one of the two reversing signals.

6. A control circuit as claimed in claim 5, wherein the latching device is a D-type flip-flop of which the D input is fed, in use, with the phase reversal signal, the clock input is fed, in use, with pulses from the frequency generator and the two outputs of which are arranged to provide the two reversing signals.

7. A control circuit for a polyphase motor, the circuit being substantially as herein described with reference to, and as illustrated by, the single figure of the accompanying drawing.

8. A electric motor connected to a control circuit as claimed in any preceding claim for control thereby.

COMPLETE SPECIFICATION This drawing Is a reproduction of the Original on a reduced scole

(54) LATEX BLEND BINDER COMPOSITIONS FOR ASBESTOS SHEETS (71) We, GAF CORPORATION, a Corporation organized and existing under the laws of the State of Delaware, United States of America, having its main office at 140 West 51st Street, New York, New York 10020, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to binder compositions for asbestos fibers and aggregates and to asbestos sheets prepared therewith.

The binder composition of this invention is a latex blend wherein the dispersed phase comprises (1) from 80 to 99.5 weight percent of a conventional synthetic rubber binder and (2) from 0.5 to 20 weight percent of a highly carboxylated copolymer or terpolymer containing repeating units based on (a) from 30 to 85 parts by weight of an unsaturated carboxylic acid of the formula:

in which R is methyl or ethyl, (b) from 5 to 50 parts by weight of an unsaturated carboxylic acid ester of the formula

in which R, is alkyl of from I to 8 carbon atoms, preferably alkyl of from I to 4 carbon atoms, and R2 is hydrogen, methyl or ethyl, and (c) from 0 to 20 parts by weight of an ethylenically unsaturated organic termonomer which is different from and copolymerizable with monomers (a) and (b) to form a stable latex.

The termonomer (c) is preferably represented by the formula

wherein R3 is hydrogen, methyl, ethyl, or halogen such as chlorine, bromine, iodine or fluorine, X1 is hydrogen or C1-C18 alkoxycarbonyl, and X2 is aryl, aminocarbonyl, cyano, C1-C4 alkoxy, carboxyl, C1-C18 alkoxycarbonyl, acyloxy, halo, acyl, aldehyde, a keto-containing group, isocyanato, C3-C9 heterocyclic, C1-C4 alkyl, C1-C4 alkenyl, halomethyl, acetomethyl, a sulfo-containing group, tri(C1-C4 alkoxy)silyl or hydrogen.

The highly carboxylated copolymer or terpolymer latex and the conventional synthetic rubber binder latex are blended to provide an excellent binder composition for use in the manufacture of bonded asbestos felts and sheets in which the fibers are uniformly coated with synthetic rubber. The product is characterised by superior interfiber bonding. Furthermore, the drainage of water from asbestos slurries containing the latex blends of this invention is greatly accelerated.

Asbestos sheets suitable for use as a substrate for vinyl flooring are generally produced with fibers ranging in length from 1/32 to 1/8 inch. Fibers with these lengths are classified by the Quebec Asbestos Producers Association as Grades 5, 6 and 7. These grades and mixtures thereof are generally used in the manufacture of asbestos sheets but other fibers, e.g., cellulose, are occasionally introduced.

The desired amount of asbestos fiber, generally from 0.3 to 8% by weight of the total slurry, is added to water to form a slurry. The slurry is then refined in a Hydropulper, Jordan engine, beater or disc refiner. The water at this point is hot (38"C.) and it is recycled from the wet end of the papermaking machinery. After the fiber bundles are broken down, the slurry is transferred to a tank where binder latex is added. The mixture is then formed into sheets and the sheets are then pressed and dried.

The conventional synthetic rubber binder latex used in the latex blends of this invention typically comprises carboxylated styrene-butadiene containing from 50 to 70 weight percent of styrene, from 30 to 50 weight percent of butadiene and from o to 5 weight percent of a carboxylic acid monomer such as acrylic acid, methylacrylic acid, fumaric acid or itaconic acid. Alternatively, the latex may contain a copolymer of acrylonitrile and butadiene, neoprene, or other synthetic rubber known in the art. Additionally, the latices may also contain emulsifiers, chain transfer agents, preservatives and other modifiers.

The highly carboxylated latices employed in the present invention are preferably prepared by a low temperature, single stage emulsion polymerization process in which all the ingredients for the polymerization are present in the reactor upon initiation of the polymerization, as described more fully below. The polymers resulting from this polymerization comprise the repeating units:

and optionally, the residue of a different ethylenically unsaturated termonomer, preferably of the formula

wherein R, R1, R2, R3, X, and X2 are as defined hereinabove.

As stated, the highly carboxylated copolymer or terpolymer contains repeating units based on the following ingredients in the following proportions: (a) From 30 to 85 parts by weight of an o,monoethylenically unsaturated carboxylic acid of Formula I, i.e. methacrylic acid, ethacrylic acid or a mixture thereof. Preferably there are from 50 to 80 parts in copolymer latices and from 50 to 70 parts in terpolymer latices. Other unsaturated carboxylic acids such as acrylic acid can be employed in admixture therewith in amounts up to 50 /O or more by weight of such mixtures depending upon the concentration and hydrophobic nature of the carboxylic acid ester units in the resulting polymer.As the concentration and/or hydrophobic nature of the ester (b) increases, increasing amounts of such other unsaturated carboxylic acids, e.g. acrylic acid, can be employed to the extent that a stable latex can still be obtained.

(b) From 5 to 50 parts by weight of at least one alkyl ester of an a-- unsaturated carboxylic acid of Formula II. Preferably at least a predominant portion of said ester has 1 to 8 carbon atoms in the alkyl moiety, and preferably from 20 to 50 parts by weight in copolymer latices, and from 20 to 30 parts in terpolymer latices.

(c) From 0 to 20 parts, preferably from 3 parts to 8 parts, by weight, of an ethylenically unsaturated organic termonomer different from monomers (a) and (b) and including such illustrative monomers as styrene, vinyltoluene, chlorostyrene, acrylamide, methacrylamide, N-isopropyl acrylamide, acrylonitrile, methacrylonitrile, vinylidene cyanide, methylvinyl ether, ethylvinylether, butyl vinyl ether, halfacid ethylmaleate, halfacid 2-ethylhexyl maleate, halfacid ethylfumarate, halfacid ethylitaconate, diethylmaleate, dibutyl maleate, diethyl fumarate, vinylchloride, vinylidene chloride, vinylbromide vinylidene fluoride, vinylacetate, vinylpropionate, vinylchloroacetate, vinylbenzoate, vinylthioacetate, acrolein, methacrolein, methylvinylketone, ethylvinylketone, isopropenyl methyl ketone, vinyl isocyanate, isopropenyl isocyanate, vinyl isothiocyanate, N-vinyl-2-pyrrolidone, N-vinyl-2-oxazolidinone, vinylfurane, indene, 2,3-dihydrofurane, vinyl succinimide, butadiene, isoprene, chloroprene, allyl chloride, allylacetate, allyl laurate, methallyl chloride, vinyl sulfonic acid, sodium vinyl sulfonate, vinyltriethoxy silane, vinyl triisopropoxy silane, ethylene and propylene.

Besides the aforedescribed termonomer types, small amounts of a bifunctional ethylenically unsaturated cross-linking monomer may also be added to the mixture.

This monomer has to be capable of polymerizing under free radical conditions so as to covalently bond different chains of the polymer. Polyfunctional monomers, such as divinyl benzene, polyethyleneglycol-dimethacrylate and methylenebisacrylamide are illustrative examples. Other monomers, which can render the polymer curable (through heat treatment) or otherwise cross-linkable, such as methylolacrylamide, glycidylmethacrylate or epoxybutadiene can also be used as additional comonomers.

The preferred method of polymerization is essentially a free radical-catalyzed batch polymerization of monomers which are dispersed in the aqueous phase with suitable surface active agents and protective colloids. A redox initiator system is recommended. The exothermic polymerization is carried out under an inert gas and is complete after a period of 10 minutes to 2 hours. The particles of the resulting latex are extremely small in size and have a high anionic surface charge.

The emulsions typically have from 10 percent and preferably from 20 percent to 50 percent solids content. The average particle size of the emulsion may be from 500 Angstroms or smaller to 3000 Angstroms or greater. The reaction temperature applied depends, in the first place, on the polymerization catalyst and the monomers used. In general, the polymerization is carried out at a temperature in the range of from 5"C to 1200C. When the catalyst is a redox system, the recommended initial temperature range is 5"C to 800C, advantageously, 150C to 60"C.

It is advisable to operate with exclusion of oxygen, for example under a neutral gas such as nitrogen or argon. Sometimes it may also be advantageous to run the reaction under elevated or reduced pressure.

The polymerization can be run conveniently by a single stage procedure, whereby all the ingredients are charged to the reactor at the same time. Since the polymerization reaction is exothermic, the initiation thereof can be evidenced by the increasing temperature resulting from the addition of the reactants. When the polymerization has proceeded to the extent that the consumption of the monomers is practically complete, the terminal point is indicated by the cessation in the rise of the temperature, followed by a temperature drop. The time period necessary for the aforedescribed operation can range from 10 minutes to 2 hours.

Chain transfer agents can be used to regulate the average molecular weight of the polymer. Preferred agents are mercaptans such as t-dodecylmercaptan.

The above preparation of the terpolymers is carried out in an emulsion system.

The term "emulsion" as used herein is intended to mean a true colloidal dispersion of the terpolymers in water.

Polymerization is effected in the presence of a catalyst or initiator, preferably one which serves as a thermally activated source of free radicals. Among such catalysts may be mentioned peracetic acid, hydrogen peroxide, persulfates, perphosphates, perborates and percarbonates. The preferred catalyst is ammonium persulfate, as it provides efficient reaction rates and contains a fugitive cation. The

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   (b) From 5 to 50 parts by weight of at least one alkyl ester of an a-- unsaturated carboxylic acid of Formula II. Preferably at least a predominant portion of said ester has 1 to 8 carbon atoms in the alkyl moiety, and preferably from 20 to 50 parts by weight in copolymer latices, and from 20 to 30 parts in terpolymer latices.

   (c) From 0 to 20 parts, preferably from 3 parts to 8 parts, by weight, of an ethylenically unsaturated organic termonomer different from monomers (a) and (b) and including such illustrative monomers as styrene, vinyltoluene, chlorostyrene, acrylamide, methacrylamide, N-isopropyl acrylamide, acrylonitrile, methacrylonitrile, vinylidene cyanide, methylvinyl ether, ethylvinylether, butyl vinyl ether, halfacid ethylmaleate, halfacid 2-ethylhexyl maleate, halfacid ethylfumarate, halfacid ethylitaconate, diethylmaleate, dibutyl maleate, diethyl fumarate, vinylchloride, vinylidene chloride, vinylbromide vinylidene fluoride, vinylacetate, vinylpropionate, vinylchloroacetate, vinylbenzoate, vinylthioacetate, acrolein, methacrolein, methylvinylketone, ethylvinylketone, isopropenyl methyl ketone, vinyl isocyanate, isopropenyl isocyanate, vinyl isothiocyanate, N-vinyl-2-pyrrolidone, N-vinyl-2-oxazolidinone, vinylfurane, indene, 2,3-dihydrofurane, vinyl succinimide, butadiene, isoprene, chloroprene, allyl chloride, allylacetate, allyl laurate, methallyl chloride, vinyl sulfonic acid, sodium vinyl sulfonate, vinyltriethoxy silane, vinyl triisopropoxy silane, ethylene and propylene.

   Besides the aforedescribed termonomer types, small amounts of a bifunctional ethylenically unsaturated cross-linking monomer may also be added to the mixture.

   This monomer has to be capable of polymerizing under free radical conditions so as to covalently bond different chains of the polymer. Polyfunctional monomers, such as divinyl benzene, polyethyleneglycol-dimethacrylate and methylenebisacrylamide are illustrative examples. Other monomers, which can render the polymer curable (through heat treatment) or otherwise cross-linkable, such as methylolacrylamide, glycidylmethacrylate or epoxybutadiene can also be used as additional comonomers.

   The preferred method of polymerization is essentially a free radical-catalyzed batch polymerization of monomers which are dispersed in the aqueous phase with suitable surface active agents and protective colloids. A redox initiator system is recommended. The exothermic polymerization is carried out under an inert gas and is complete after a period of 10 minutes to 2 hours. The particles of the resulting latex are extremely small in size and have a high anionic surface charge.

   The emulsions typically have from 10 percent and preferably from 20 percent to 50 percent solids content. The average particle size of the emulsion may be from 500 Angstroms or smaller to 3000 Angstroms or greater. The reaction temperature applied depends, in the first place, on the polymerization catalyst and the monomers used. In general, the polymerization is carried out at a temperature in the range of from 5"C to 1200C. When the catalyst is a redox system, the recommended initial temperature range is 5"C to 800C, advantageously, 150C to 60"C.

   It is advisable to operate with exclusion of oxygen, for example under a neutral gas such as nitrogen or argon. Sometimes it may also be advantageous to run the reaction under elevated or reduced pressure.

   The polymerization can be run conveniently by a single stage procedure, whereby all the ingredients are charged to the reactor at the same time. Since the polymerization reaction is exothermic, the initiation thereof can be evidenced by the increasing temperature resulting from the addition of the reactants. When the polymerization has proceeded to the extent that the consumption of the monomers is practically complete, the terminal point is indicated by the cessation in the rise of the temperature, followed by a temperature drop. The time period necessary for the aforedescribed operation can range from 10 minutes to 2 hours.

   Chain transfer agents can be used to regulate the average molecular weight of the polymer. Preferred agents are mercaptans such as t-dodecylmercaptan.

   The above preparation of the terpolymers is carried out in an emulsion system.

   The term "emulsion" as used herein is intended to mean a true colloidal dispersion of the terpolymers in water.

   Polymerization is effected in the presence of a catalyst or initiator, preferably one which serves as a thermally activated source of free radicals. Among such catalysts may be mentioned peracetic acid, hydrogen peroxide, persulfates, perphosphates, perborates and percarbonates. The preferred catalyst is ammonium persulfate, as it provides efficient reaction rates and contains a fugitive cation. The

   amount of initiator used is normally 0.03 to 3.0 percent by weight of the total monomers and preferably from 0.25 to 0.5 percent. Preferably the initiator is a redox combination of the water soluble persulfate as the oxidizing component and a hydrosulfite, e.g., sodium hydrosulfite, as the reducing component of the redox combination. Water soluble bisulfites, metabisulfites or thiosulfates, reducing sugars or formaldehyde sulfoxylate may be used in lieu of the hydrosulfites. Other typical redox combinations, such as sodium azide and ceric ammonium sulfate, titanium trichloride and hydroxylamine may also be used. Generally useful proportions of the indicated persulfate-hydrosulfite system are from 0.01 to 1.0 percent for the oxidizing component and from 0.15 to 1.5 percent for the reducing component based on the amount of monomers.

   The redox combination can be further activated by the presence of polyvalent metal ions at the lower oxidation stage, e.g., ferrous sulfate or cuprous sulfate. The preferred amount of these metal salts may be between 5 ppm and 10 ppm by weight, based on the total amount of the monomers.

   The aqueous medium for polymerization contains some emulsifiers to help to disperse the monomers in the aqueous medium, and to protect the particles formed. Salts of the higher molecular weight sulfonic acids, e.g., alkyl aryl sodium sulfonates, are eminently suitable for the purpose, though other surfactants may also be used with good results.

   The amount of surfactant employed can be varied considerably, but ordinarily from 0.1 percent to 10 percent, and more particularly from 0.2 percent to 1.0 percent, by weight, based on the total weight of the comonomers, will be used.

   Additives such as alcohols can also be used in order to enhance the solubilization of the water insoluble ingredients. The concentration of these materials can be varied between 0.1 percent and
2. 2.0 percent by weight, based on the weight of the comonomers. The emulsion can also contain a small amount of a protective colloid, such as water soluble cellulose derivatives, poly(vinylpyrrolidone), alkali metal polyacrylates or water soluble alginates. The amount of such a colloid used can range, for example, from 0.1 percent to 2 percent and more particularly from 0.5 percent to 1 percent.

   Only a small amount of highly carboxylated latex is required to produce significant improvements in the physical properties of the slurry and the finished sheet. The highly carboxylated latex may be blended with conventional rubber binder latex provided that the two are compatible. Such blends may contain as little as 0.5 parts to as much as 20 parts of the highly carboxylated additive polymer in 100 parts of the dry weight. The preferred amount of highly carboxylated polymer is from 1 part to 8 parts in 100 parts of the total polymer dry weight. The resulting slurry with asbestos and 15 parts of binder will contain from 20 ppm to 800 ppm of highly carboxylated polymer. The exact amount of highly carboxylated polymer needed to achieve the desired performance characteristics will depend on the properties of the binder latex with which it is blended.

   Latices for asbestos felts are evaluated by preparing hand sheets and subjecting them to conventional paper testing. A blend of 25 parts of Quebec grade 5 and 75 parts of Quebec grade 7 asbestos is dispersed in water (38"C) to about a 5% consistency. The slurry is agitated using a 2.5 inch split disc impeller at 1000 rpms for 8 minutes. Sufficient latexis added to give 15 parts of polymer in 100 parts of asbestos and the stirring continued for 7 minutes. The resulting slurry is uniform and homogeneous and suitable for forming sheets in a Williams sheet mold after being diluted to a 3% consistency. The sheets are then pressed on a Williams hydraulic press and dried on the Williams standard sheet dryer.

   Water (350C) is added to the stock to bring the consistancy to 2%. The drainage of water from the asbestos slurries is measured with a Schopper-Riegler freeness tester. Low numbers indicate fast drainage.

   The tensile strengths are determined by pulling I inch strips of the sheet on an Instron 1130 test instrument at a crosshead speed of 2 in/min ("Instron" is a Registered Trade Mark). A cold test is done at room temperature (210C); a hot test is done by heating the strip to 1900C; a plasticizer tensile is run after the sample is soaked for 18 hours in butyl benzyl phthalate to simulate the plasticizers which may be used in some vinyl coatings in flooring manufacture.

   In the following examples, all parts, percentages, proportions and other quantities are by weight unless otherwise indicated.