CA1044836A - Thermosetting vinyl halide emulsion copolymers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Vinyl halide emulsion copolymers are modified to introduce improved thermosetting cure capacity by including in the copolymer a proportion of a formaldehyde addition product with an allyl carbamate.

Description

~ 4 ~ ~
The present invention relates to emulsion copolymers of vinyl halides, such as vinyl chloride, with ethylene or monoethylenic ester which has been modified to introduce improved thermosetting cure capacity. These emulsion copoly-mers are known to be useful as binders for nonwoven fabrics, as impregnants for woven fabrics, as a binder in printing pastes, as laminating adhesives, as paints, and for other similar purposes. These emulsion polymers are illustrated, for example, by United States Patent 3,647,615 where N-methylol acrylamide is used to modify vinyl chloride copoly-mers in order to provide the desired curing characteristics.
This invention has,as its main objective, the achievement of improved cure characteristics, which can be demonstrated by the achievement of increased insolubilization after cure.
In connection with the thermosetting characteris-tics which it is desired to achieve in accordance with the invention, the increased insolubilization which is achieved leads to many important benefits. With particular reference to fabrics which have been treated with the emulsions of the invention and then baked in order to cure the deposited copoly-mer, wash resistance and crocking are improved when the emul-sion is used as a binder in a printing paste, nonwoven web integrity is improved when the emulsion is used as a binder for a nonwoven web, durability to washing is improved when the emulsion is used to modify the hand of a woven fabric, wash and solvent resistance are improved when the emulsion is used in a foam applied to a fabric to serve as a drapery backing, and peel strength is improved when the emulsion is used for laminating purpose. It is stressed that vinyl halides, such as vinyl chloride and ethylene, polymerize poorly from the

-2- ~

iV~4~
standpoint of achicving desircd hi~h molecular woight, makin~ the i~roved distribut;on of cross-lin~ing obtained herein of especial significance.
As will be appreciated, the invention, likc the prior art, is concerned with aqueous emulsions in which the aqueous medium has colloidally suspended there;n an emulsioll copolymer of vinyl halide, which has becn modified to provide the propertics noted abovc.
Copolymers with ethylene arc ~articularly contcmplnted.
~ n accordance with the invention, an aqueous cmulsion com-prising an aqueous medium having colloidally suspended therein an emulsion copolymer of from 35% to 96.5% of vinyl chloride, from 3% to 60% of ethylene, and from 0.5 to 15% of monomers providing ther -setting characteristics and comprising at least 0.5% of the N-methylol functional addition product of formaldehyde with an allyl carbamate having the formula ,Rl O / H
2 C CH2 o ~ R20 ~ H

in which Rl is hydrogen or methyl, R2 is an alkylidene group containing from 2-4 carbon atoms, and n is an integer from 0-10, preferably from 0-2, and most preferably 0.
Yarious allyl carbamates are useful herein, especially allyl carbamate. Allyl carbamate has the formula ,0, / H
CH2=CH-CH2-0-C-N ~ ' :
This monoethylenic monomer is not an amide and it will react with formaldehyde in an addition reaction with the two amino hydrogen atoms to generate the N-methylol group. When one molar proportion of formaldehyde is taken up, the derivative can be described by the formula O / H
CH2=cH-cH2-o-c-N

1~

The s~me reaction can proceed to tak~ up more formaldehyde to increase the N-methylol functionality ~hich is generated.
Regardless of whether one or two moles of for~alde-hyde are reacted into the molecule, the monomer is an allyl ester and this is most important in the copolymerization with vinyl halide, since the monomer reactivity ratio of the allylic ~nsaturation of the allyl ester with vinyl halide is close to 1:1. In contrast, methylol acrylami.de enters thc vinyl halide copolymer much too rapidly, forcing a considerable portion of the polymer to lack the reactive group which is the basis for subsequent insolubili~ation~
The emulsion copolymerization is also improved herein by the increased hydrophobicity conferred by the allyl group creating a synergis~ic improvement in the capacity of the copolymer to become insolubilized on curing. Such hydrophobicity can also be enhanced by employing an ether group, as will be explained.
As previously indicated, the allyl carbamate may include ether groups between the allyl group and the carbama~e group. These ethers can be provided by reacting the allyl alcohol with an al~ylene oxide, such as ethylene oxide before converting the resulting alcohol to the carbamate as will be illustrated hereinarter.
The adduction of the carbamate with formald~hyde is ~ell known and conventional and yields N-methylol d~rivatives.
These are a mixture of the mono-N-methylol adduct, the di-N-methylol adduct and unreacted carbamate which, if present, is not ha~mful.

. ,, .; .

~u~

The N-methylol groups in this invention may be etherified with a Cl - C8 alcohol, preferably a Cl - C4 alcohol, though this is not essential. The alcohol is released on baking to regenerate the N-methylol group for cure, as is well known. Appropriate alcohols for etherifi-cation are methyl alcohol and ethyl alcohol. Isopropyl alcohol, isobutyl alcohol, 2-ethoxy ethanol and 2-butoxy ethanol will further illustrate useful alcohols.
The invention is applicable to vinyl halides.
Among the halides, the chlorides are most commonly avail-able, and are most economical so that this invention is primarily addressed to the use of vinyl chloride. On the other hand, the corresponding bromides introduce superior fire resistance and, when this characteristic is important, the bromides may be used. Similarly, the corresponding fluorides provide polymers which are very inert and, when it is desired to obtain maximum corrosion resistance and ~ .
durability, the corresponding fluorides may be used. The iodides are also subject to use in this invention, but these ~ ~-would only be used to provide special properties. Of course, the different halides are also useful in admixture.
Also, and while copolymers with ethylene are especially important, the invention includes copolymers in which the ethylene is partially replaced with a mono-ethylenic carboxylic acid ester which provides the desired internal plasticization. The ester group will contain a terminal saturated hydrocarbon group having at least 2 carbon atoms, preferably at least 4 carbon atoms, and is usually an alkyl ester of an alpha,beta-ethylenically unsaturated acid such as maleic acid, fumaric acid, acrylic acid, crotonic acid, itaconic acid, and the like. These are illustrated by butyl acrylate, diethyl maleate, and isooctyl crotonate. Other esters such as vinyl hexoate are also useful, though less preferred. The ester group may contain up to about 18 carbon atoms.
From the standpoint of proportions, the vinyl halide will constitute from 35-96.5% of the copolymer, pre-ferably 45-75%. The ethylene component will constitute from

3-60%, preferably from 10-45%, and most preferably from 20-40%. Of course, mixtures of ethylene and ester in the same total amount can be used.
The monomers providing thermosetting or cure capacity may be used in an amount of from 0.5-15%, preferably 2-10%, based on the weight of the copolymer. At least 0.5%, prefer-ably at least 1%, based on the weight of the copolymer, will be constituted by the formaldehyde addition product with the allyl carbamate compound, preferably from 1% to 8%. However, other monomers which can coreact with the N-methylol group -may also be present to assist in the cure, such as monoethylenic amides or alcohols, either alone or together with one another or with a monoethylenic carboxylic acid.
The coreactive monomers are illustrated by acryl-amide, methacrylamide, or other monoethylenic amide, or by allyl alcohol, 2-hydroxy ethyl acrylate or methacrylate, or the like. Monoethylenic carboxylic acids are illustrated by acrylic acid, methacrylic acid, and crotonic acid. These acids are used in an amount of from 0.5-3%.
Other monomers which may be present in an amount up to about 20% of the copolymer are illustrated by acrylonitrile, methyl methacrylate, styrene, or vinyl acetate.

~v'~
Since the aqueous emulsion polymerization of vinyl chloride either alone or with ethylene or esters such as butyl acrylate is well known per se, it will not be described at length. However, it is stressed that the N-methylol allyl carbamate is easier to use since it will enter the copolymer at about the same rate as the vinyl halide so that the distribution of the N-methylol group in the final copolymer is considerably improved. Auxiliary agents may also be present, as is known, such as protective colloids, illustrated by poly-vinyl alcohol and hydroxy ethyl cellulose.
From the standpoint of cure, baking is normally carried out at temperatures of from 250-500F. for periods of from 30 seconds to 1 hour, but more usually at 275-350F.
for from 2-20 minutes.
The proportions referred to herein and throughout this specification are by weight unless otherwise specified.
Example 1 Monomer Emulsion (100% charged) Parts Vinyl Chloride tDistilled) 12000 grams Sodium Lauryl Sulfate (30% water Solution) 1695 "
Dioctyl Ester of Sodium Sulfo Succinic Acid in a 60% Water Solution 847 "
Acrylamide (16.9% in Water) 2600 "
N-Methylol Allyl Carbamate (16.9% in Water) 2600 "
A stainless steel pressure reactor equipped with temperature controls and an agitator was charged with:
Charge Parts Water 10400 grams Sodium Lauryl Sulfate (30% Water Solution) 565 "
Dioctyl Ester of Sodium Sulfo-succinic Acid in a 60% Water Solution 282 "

, . " , . .

lV44~
Charge and Parts (continued) Previously Prepared Seed Polymer Emulsion at 45% Total Solids (Use previous batch of this Example or commercial polyvinyl chloride of particle size .15 micron) 760 grams Ferrous Sulfate 0.15 "
Maleic Anhydride ~5 "
Monomer Emulsion of this Example 1850 "
Sodium Persulfate 55 "
The reactor was purged with nitrogen, then with ethylene, after which the reactor was pressurized to 60 atmospheres with ethylene. After heating the reactor mixture to 50C., 5cc of a 6% water solution of sodium formaldehyde sulfoxylate were added, after which the reactor temperature rose to 53C. The remaining monomer emulsion (to 100% of the total amount prepared) was added continuously over a five hour period. The reaction temperature was maintained exothermic by incremental additions of a totalamount of 195cc of a 6%
sodium formaldehyde sulfoxylate solution, and 750cc of a 10% sodium persulfate solution. The ethylene pressure was maintained at 60 atmospheres during most of the run, and then the ethylene pressure was slowly reduced to atmospheric pressure, and the pH was adjusted to 5.3 with ammonia.
The product had the following properties:
Viscosity (#3 spindle, 30 rpm Brookfield) 1000 Solids 37.5%
Intrinsic Viscosity (measured in 1%
dimethyl formamide at 30C. and extrapolated to 0%) 1.24 Insolubles at pH 2.7 55.1%
at pH 8.0 52.8%
pH 5.2 ~ 4 ~ ~

Average Particle Size 0.225 micron Ethylene in Copolymer 45%
Example 2 Example 1 was repeated, replacing the N-methylol allyl carbamate with a corresponding weight of N-ethoxy methyl allyl carbamate. The final produced cured to provide even better insolubility~

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An aqueous emulsion comprising an aqueous medium having colloidally suspended therein an emulsion copolymer of from 35% to 96.5% of vinyl chloride, from 3%
to 60% of ethylene, and from 0.5% to 15% of monomers providing thermosetting characteristics and comprising at least 0.5% of the N-methylol functional addition product of formaldehyde with an allyl carbamate having the formula:

in which R1 is hydrogen or methyl, R2 is an alkylidene group containing from 2-4 carbon atoms, and n is an integer from 0-10.

2. An aqueous emulsion as recited in claim 1 in which said allyl carbamate addition product is mono-N-methylol allyl carbamate.

3. An aqueous emulsion as recited in claim 1 in which said copolymer consists of from 45% to 75% of vinyl chloride, from 10% to 45% of ethylene, and from 2% to 10% of monomers providing thermosetting characteristics and comprising at least 1% of N-methylol allyl carbamate.

4. An aqueous emulsion as recited in claim 1 in which said addition product contains from 1-2 moles of formaldehyde per mole of said carbamate.

5. An emulsion as recited in claim 1 in which said copolymer further includes from 0.5% to 3% of a monoethylenic carboxylic acid.

6. An emulsion as recited in claim 1 in which n is 0.

7. An emulsion as recited in claim 1 in which said N-methylol functional addition product is etherified with a C1 - C8 alcohol.

8. An emulsion as recited in claim 1 in which said monomers providing thermosetting characteristics include an acrylamide.