The Centrene F was prepared by esterifying 3 moles of ethylene glycol lvith 2 moles of maleic anhydride and eliminating 2 moles of water: 0
’
HC-C
2l HC-C
/
‘ 0
/ b
+ 3HO-CH?CH2-OH Gs+
0 0
‘I
0
HQCH~-CH~-O-C-CH=CH-CC-O-CH~
0 HO-CH
11
2-CH ~-0-C-CH=CH-C-O-CH
linked products therefrom were more brittle than typical industrial grades of polyesters. Many other Endene compositions have been tested-for example, chains terminated by fumarate or maleate esters of methyl or allyl alcohols. Glycol or ether terminals have also been used. These were compared with the Centrenes or Ivith polyesters having a random distribution of unsaturation. The Endenes had superior physical properties compared xvith the other isomers. It is believed that application of the Endene principle will show similar relationship for other types of polymers and is not restricted to polyesters.
I
0
I
1
4 2H20 2
In Endene E, maleic acid moieties, having double bonds, constitute the terminals, while in Centrene F the ethylene glycol terminals displace the double bonds more toward the center of the molecule. These two structural isomers were cured with styrene and with diallyl phthalate, yielding hard. brittle resins. Many samples, especially those cured with styrene, broke in testing; thus, physical test data are available only on the diallyl phthalate cures. Comparison (Table 111) shows the superiority of Endene over Centrene structure. These polyesters are Ion- in molecular \%-eight. Thus the cross-
Acknowledgment
I thank P. J. Flory for his helpful suggestions and comments in the preparation of this paper, and Albert W. Kacmarik for his able assistance in the preparative phases of these studies. Literature Cited fl) Carlston. E. F.. Johnson. G. B.. Lum. F. G.., Huwins. D. G.. -0 > Park, I(.T., Ind. Eng. Chem. 51, 253 (1959). (2) Flory, P. J., J.Am. Chem. SOC. 58, 1877 (1936). (3) Guth, E., Mark, H., Monatsh. 65, 93 (1934). (4) Szayna, .4., U. S. Patent 2,889,312 (1959). \
,
RECEIVED for review November 19, 1962. ACCEPTED February 6, 1963 Contribution 229, Research Center, U. S. Rubber Co.
BINDERS FOR NONWOVEN FABRICS Evaluation of Binders Based on Copolymers of Vinyl Acetate R.
L. A D E L M A N , G. G. ALLEN,’ A N D
Research Division,Electrochemicais Department, E. I. du Pont de .\‘emours
H. K. S l N C L A l R Go., Inc., Wilmington, Del.
A procedure was developed for a preliminary evaluation of binders for drapable, durable nonwoven fabrics. This was based on coagulation of the binder from solution or emulsion within a performed random web, followed b y a compression molding step. The important variables in this procedure are discussed. Some generalizations are presented relating binder-fiber distribution and binder molecular structure with properties of the resulting nonwoven fabrics. Certain vinyl acetate copolymers appear to be generally equivalent to all-acrylate systems in bonding performance.
on nonwoven fabrics has been aimed a t obtaining a better understanding of the factors involved which could lead to fabrics Lvith improved esthetics and performance. Of particular interest are the effects of variations of molecular structure on fabric properties and in synthesizing new binders for nonTvoven fabrics. Polymers based on acrylate esters and containing small amounts of carboxyl groups are \veil known and commonly used binders for durable non\voven fabrics (70, 73). These have advdntages over other reported loit modulus binder systems, such as the butadiene-styrene or butadiene-acrylonitrile elastomers, demonstrating greater bond strength, less color, and better aging properties. Hoiveiver, the acrylate polymers are considered somelvhat high in cost. ESEARCH
Present address, Weyerhaeuser Timber Co., 41 3 Stoneway, Seattle 13, Wash. 108
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
Pol! mers based on v i q l acetate appear to be very similar to the polyacrylates in polar and adhesive character as well as in lack of color and excellent aging characteristics. This has been indicated in many adhesive, textile finish, and pigment binder applications. In addition, the poly(viny1 acetates) have a significant cost advantage over the acrylates, which has led to their use as binders for “disposable” nonwovens, with the fabrics demonstrating good strength and water resistance under moderate temperature conditions. For high strength, drapable, durable fabrics, binders based on polymers of vinyl acetate led KO fabrics which were too solvent-sensitive or too \vater-sensiti\ e for durability in dry cleaning or laundering operations (3, 12, 73). Also such polymers have lacked resilience and had marginal adhesion values. However, there are essentially no quantitative comparisons in the literature in which the chemical composition of the binder is related to fabric properties.
This article describes a procedure for a preliminary evaluation of binders for drapable, durable nonwoven fabrics and compares the binder performance of certain copolymers of vinyl acetate, specifically prepared for use in this area, with all-acrylate binder systems. Experimental
Preparation of Binders. Vinyl acetate copolymerizations Lvere carried out in both aqueous dispersion and solution. Pure batch and continuous monomer addition techniques trere both employed. Polymers of various molecular weight were prepared by the use of dodecyl mercaptan or chain-transfer solvents. Homogeneous copolymers with regard to composition were obtained by analysis of the polymer a t different degrees of conversion, followed by adjustment of the monomer feed rates. All-acrylate copolymers were prepared in aqueous dispersion in similar fashion. Use of Randoweb. Random webs of 6.6-nylon staple [Type 200,3 denier per filament (d.p.f.), l'/?inches cut length]. Egyptian cotton staple (scoured, bleached, filter grade), and Dacron polyester fiberfill staple (2 inches cut length fibers, 8 crimps per inch, 4.75 d.p.f.. greater than 3 grams per denier) were used to make fabric samples as orthotropic as possible in the lengthwise and crossicise directions. This permitted a sizable reduction in the number of measurements. The \\-ebs \\-ere prepared a t a \\-eight of 2.7 ounces per sq. yd. on a Curlator Corp. Randowebber and were of reasonable homogeneity (see Physical Testing Procedures). Preparation of t h e Fabrics. A weighed sample of the web (about 9 X 9 inches) was supported on both sides with 14 X 14 inches bronze screens (16-mesh), and the assembly was immersed a t room temperature in a solution of the binder dissolved in a n organic solvent (tetrahydrofuran or acetone) or a n aqueous dispersion of the binder in water. After immersion for about 30 seconds, the assembly was lifted out of the solution, passed rapidly through a handwringer (fitted with neoprene rollers) to remove excess binder. and then either submerged in a coagulating bath of nonsolvent (water or aqueous salt solution), or exposed to freezing and/or high temperature conditions. T h e assembly was then again passed through the wringer, the supporting screens Lvere carefully removed from the impregnated web, and the web was dried a t 110' to 120' C. for 5 minutes. The dried. relatively bulky fabric was then generally heat-pressed bet\veen Armalon TFE-fluorocarbon coated glass fabrics (E. I. du Pont de Nemours gL Co., Inc.) and/or 40-meshstain less steel screens. When vigorous curing v'as necessary, curing conditions for the fabrics of nylon and Dacron polyester fiber were 200" C.. for 3 minutes, a t 5 to 25 tons platen pressures. For noncured cases and for cotton fabrics, heating was carried out a t 135" C. for 15 minutes. The wringer had been modified to permit a knoirn adjustable force to 6 to 60 pounds to be applied to the lower roll. The amount of binder pickup in the web was very responsive to the roller pressure and the solids concentration in the solution. In general, fabric samples were prepared using polymer solutions with similar solution viscosities and roller pressures, so that variations in fiber penetration by the binder solutions would be minimized. In a few cases, where the binders were insoluble in tetrahydrofuran or methanol but soluble in toluene, the binders were coagulated inside the web from toluene solution with methanol. Although impregnation of webs from organic solvents is not common practice in the nonwoven industry, advantages exist for this technique in a laboratory comparison of binder
candidates, and results should be capable of extension to other types of nonwoven fabric structures and methods of preparation. These advantages include the folloiving : Different types of polymeric binders prepared in various fashions (dispersion, bead, solution, etc.) can be applied with similar morphologies and distributions in the fiber web. Microscopic examination of a fabric under tension showed the binder to be made up of filmy areas and strands connecting fibers, most ofwhich had partially uncovered surfaces. T h e binders and the fibers may be freed of various wetting agents, protective colloids, etc., before application, which may seriously affect the adhesion values and water resistance of the fabric bonds. Because of the highly tacky, adhesive nature of the polymer produced by the coagulation step, no significant lamination occurs in the fabric structure owing to binder migration. Physical Testing Procedures. The evaluation of binders for nonwoven fabrics is complicated by the varied fabric requirements for different fields of application. In the area of lightweight apparel nonwovens, contributors to the literature appear to agree on high fabric strength and durability, with low bending rigidity (related to good drape and softness), as key property criteria, a t competitive cost with Lvoven fabrics (2: 8). For initial screening purposes, certain fabric properties were determined : DRYBREAKSTRESGTH A N D PERCENTELONGATION AT BREAK
(ASTM D1117-53) were determined using a modified cut-strip method. All fabrics \\-ere given a preliminary wash in 0.2Tc Tide solution for 10 minutes a t 160' F., to remove inorganic salts from the curing formulation, and dried a t 110' C. on a Noble-Wood hot plate. Six specimens, 3 inches in length and '/2 inch wide, were cut out with a precision cutter with the long axis of the sample in the direction of pull of the fabric through the wringer. T h e specimens after conditioning 24 hours a t 70' F., 50%) R.H.. were pulled in a n Instron tester with a 2-inch jaw separation a t a strain rate of 50% per minute. \VET BREAKSTRENGTHS Lvere determined as for Dry Break Strength aftrr pieces xvere washed for 1 hour in lYG Tide a t the boil, and either cooled to 70" F., rinsed, and measured water-wet; or cooled to 160' F.: rinsed, and measured \vet. PERCLENE PERCHLOROETHYLENE BREAKSTRENGTH \\-as determined as for Dry Break Strength, after pieces were submerged in Perclene (E. I . d u Pont de Nemours Pr Co., Inc.) a t 70' F. for 2 hours, and measured wet. TOXGUE TEAR\vas a modified ASTM technique (D39-49: par. 16). Test specimens were 2l/2 X 2 inches. The '/l-inch cut in the fabric was made parallel to the direction of pull of the fabric b!. the Instron. Jaw separation was 2 inches, and run a t 5 inches per minute. In later work, the speed of ja\v separation was increased to 12 inches per minute. DRAPESTIFFNESS was determined by the single Cantilever method (ASTM D1388-55T, Method A). Samples 6 X 1 inches were used (cut out in the direction of pull of the fabric through the wringer), and results were expressed as "length of overhang" (the length in inches of fabric hanging over the edge of a horizontal surface and just touching a n inclined plane a t a n angle of 41.5') and a "flexural rigidity," G, in ounces-inches [equal to \V X (length of overhang) 3 / ~ , where W = weight per unit area of the fabric in ounces per square yard]. Low values of length of overhang and flexural rigidity indicate limpness, and are associated with good drape. Many fabric properties are greatly dependent on binder loading. For example. the tensile, tear, and elon ation values generally go through a maximum between 25k and 45% loading, depending on the binder distribution in the web (6, 7, 9 ) . As a result. we have compared all fabric properties a t equivalent binder loadings, which generally were a t 3070. These property values \rere calculated by interpolation of values obtained for fabrics containing 20 to 30y0 binder and 30 to 40% binder. Similarly? variations in fabric properties due to changes in fiber tenacity, diameter, and length, and variations in sheet weight (6, 9 ) can be discounted by using the same batch of web for the series of binders under investigation. Also, VOL. 2
NO. 2
JUNE 1963
109
Table 1.
Binder, Mol. Wt. Higha Lo+ Medium High
Polymerization Type Solution Solution Aq. disp., cationic Aq. disp., nonionic [poly(vinyl alcohol), low temp.] High Aq. disp., nonionic [poly(vinyl alcohol), high temp.] High Aq. disp. nonionic [poly(vinyl alcohol), high temp.] High Aq. disp., nonionic [poly(vinyl alcohol), high temp.] High Aq. disp., nonionic (hydroxyethyl cellulose; Tergitol NPX, high temp.) M , = 600,000. M , = 70,000.
Poly(viny1 Acetate)-Bonded Cotton Fabrics
30 30 19 18
Method of Application Coagulation Coagulation Coagulation Coagulation
Fabric Properties Break Strength, Elongation, % Lb./In./Oz./Sq. Yd. Dry Wet Ratio Dry Wet 6.0 5.0 0.8 12 21 0.7 16 26 0.6 0.4 12 31 1 .o 0.5 2.0 0.5 8 17 4.9 2.3
20
Coagulation
2.7
0.6
0.2
20
Padding
6.0
0.5
0.08
30
Padding
7.3
0.6
30
Padding
5.6
1 .o
Binder Loading,
%
Moffett (9) and Drelich ( 4 ) have shown that changes in binder distribution in the fabric lead to changes in fabric properties. Because of differences in flow properties of various thermoplastic binder systems at elevated temperatures and pressures, presscuring of the fabrics under equivalent conditions, as we have done in our work here, could lead to apparent differences in binder performance which would disappear a t more appropriate heat-pressing conditions. However, with the thermosetting binder systems developed in this work, relatively little binder flow occurs under the present curing conditions. Variations in binder distribution are thus minimized. Degree of Variability i n Testing. .4statistically designed group of nonwoven fabrics was prepared with the nylon Randoweb and a representative binder. With an analysis of two fabrics and three samples from each, with 95% confidence, dry break values were within +1.1 pound/inch/ ounce,/sq. yd., \vet Tide (70’ F.) break 5 0 . 9 pound/inch/ ounce/sq. yd., tongue tear 1 0 . 3 pound, ounce/sq. yd., drape stiffness (length of overhang) i0.4 inch, dry break-stiffness ratio +0.3. Somewhat lower precision was obtained with one fabric and six samples therefrom.
Tear, 16. i o z . /’ sq. yd. 2.5 0.3 1.2 1.1
10
24
1.1
0.08
6
26
0.9
0.2
5
46
0.4
amples Ivere prepared in aqueous dispersion in the presence of surface active agents, but were applied in the same way to the fabric as the solution polymer cases by isolation, purification, solution in a n organic solvent, and application to the web by coagulation. Furthermore, when a high molecular weight protective colloid such as poly(viny1 alcohol) is present under vigorous polymerization conditions (Entry 5, Table I), the dry strength drops, and the wet-dry strength ratio drops even further-from 50 to 20%. Hartley (5) and Okamura ( 7 7 ) have shown that the poly(viny1 alcohol) readily undergoes grafting with the poly(viny1 acetate) under these conditions. Also, when the binders are applied by padding the web with aqueous dispersions of the polymer, followed by evaporation of the water phase without coagulation, an even more watersensitive fabric results (wet-dry ratio of 0.08) than when applied from organic solvents (Entries 6-8, Table I). This is to be expected, as even the ungrafted protective colloid remains on the fabric in this case.
Results
Effects of Polymerization Conditions on Fabric Properties. Table I gives a comparison of the performance of several fabrics bonded with poly(viny1 acetates) of different molecular weight, with different methods of preparation of the binder and the fabric, and at different binder loadings in the web. The first two examples were prepared by solution polymerization and used as binders for cotton web by coagulation from organic solvent into water. The high molecular weight binder led to enhanced strength of the fabric, and may reflect the higher tensile strength of this binder. The magnitude of the web break strength of these fabrics, measured a t room temperature, is a t least 70 to 80% of the dry break strength. I n work not given here, we also have found that the wet-dry strength ratio is relatively insensitive to binder loading. When the polymers prepared in solution are compared with polymers prepared in aqueous dispersions, the dry strength of the latter is lowered as expected for the reduced loading of binder in the fabric, but also a decrease in wet-dry strength ratio from 7080% to 50% is evident (Entries 3 and 4, Table I). These ex110
l & E C P R O D U C T RESEARCH A N D D E V E L O P M E N T
FLEXURAL RIGIDITY OF FABRIC (IN.-OZ.I
Figure 1.
Dacron polyester fiber nonwoven fabrics
Inilial modulus of binder
VI.
flexural rigidity of fabric
Effects of Binder Cure Table II.
Cotton Webs Bonded with Vinyl Acetate Polymers
(Relative effecliveness of copolymer VI. externally plasticized homopolymer)
Fabric Break Fabric Binder y~by Strength. Stiyness, Composition Weight % Dry Inches 87-13 VAc-VPel" 100 29 4.3 7.8 20 2.7 6.4 PVAc-Kronisol 94-6 29 3.3 7.6 20 1.8 6.3 e Abbreaiations for use in this and subsequent tables are as follows: VAc = isin$ acitate. VPel = uinvl pelargonate. P V A c = poly(viny1 acetatd. DBM = dibutyl maleate. A A = acrylic acid. 2EHA = 2-ethylhexyl acrylate. B.4 = butyl acrylate. EA = ethyl acrylate. D B F = dibutyl fumarate. .MA = methyl aqylate. Vinyl acetate copolynirr "A" = a polymer based on vinyl acetate containing acrylic esters and acrylic acid. Binder Loading,
Effects of Binder Modulus. Ll'hen fabric drape and durabilitv also are important considerations, then the binder stiffness becomes significant. Figure 1 shows the flexural rigidity of a Dacron polyester fiber fabric us. the logarithm of the binder initial modulus for a wide variety of binders at a fixed binder loading. .4 fairly good correlation is evident: the greater the modulus of the binder, the stiffer the fabric. Thus for drapable fabrics. binders of low modulus should be used. However. binders cannot be used which are externally plasticized if fabrics are to retain drape after exposure to dry cleaning solvents. Therefore, copolymers of vinyl acetate with high levels of internally plasticizing comonomers were investigated. In addition. internally plasticized copolymers, such as an 87/13 vinyl acetate-vinyl pelargonate copolymer, appeared to give fabrics with higher strength-stiffness ratios than a n externally plasticized homopolymer of equivalent molecular weight which was plasticized to equivalent stiffness values with dibutoxyethyl phthalate (Kronisol, F M C Corp.) (Table 11).
Table 111.
For maintenance of fabric strength on exposure to hot aqueous soap or detergent solutions and dry cleaning solvents, vinyl acetate polymers quite generally require curing treatments. Moderate cures were obtained by heat treatments when the polymers contained small amounts of functional comonomers, such as acrylic acid, glycidyl methacrylate, or methylol acrylamide. For satisfactory levels of cure, however, both the vinyl acetate copolymers and ethyl acrylate-acrylic acid copolymers require the use of additional curing components in the formulation (70, 13). The vinyl acetate copolymer binders required more vigorous curing conditions than the ethyl acrylate copolymers. Thus for binders applied from solution, small amounts of a mineral acid catalyst were required to obtain maximum fabric properties with the vinyl acetate polymers, while acrylate-bonded fabrics were essentially unaffected by the change in cure conditions. This is indicated in Table 111, in tvhich two vinyl acetate terpolymers are compared with a commercial acrylate binder, Rhoplex B-15 (Rohm & Haas Co.). The fabrics were submitted to mild curing conditions. Acrylic acid was used in these examples as the postcurable comonomer for a good comparison with the acrylate binder. (The actual compositions of commercial acrylate binders such as Rhoplex B-I 5 have not been published, but we have obtained essentially equivalent results to Rhoplex B-I 5 with carboxylated acrylate ester copolymers such as the 92-6-2 ethyl acrylate-methyl acrylateacrylic acid terpolymer or a 98-2 ethyl acrylate-acrylic acid copolymer.) The polymer compositions compared in Table I11 were chosen empirically to give essentially the same fabric flexibility after cure as was obtained with the Rhoplex B-15. Results show equivalent dry strength but poorer fabric resistance to water and solvents using the vinyl acetate terpolymer binders. On the other hand, with a more vigorous curing treatment, the addition of 0.5 part of mineral acid (butyl phosphoric acid) per 100 parts of resin, the vinyl acetate-based
Nylon Randowebs Bonded with Cured Ethyl Acrylate, Vinyl Acetate Copolymers ( 3 9 % binder in fabric)
Binder
Curea
Acrylate binder Acrylate binder VAc-DBM-AA* 49 49 2 VAc-2EHA-AA 58 40 2
Mild
7inh
Mild
2.45 2.45 0.35
Mild
0.49
Vigorous
Break Strength, Lb./In./Or./Sq. Yd. Perclene Tide W a s h Wash Wet Dry Wet ( 7 2 ' F . ) (70OF.) 8.7 1.1 7.0 f0.9 3 . 0 3= 0 . 5 8.9 >6.7 3.0 9.9 5.7 1.4
*
7.9
5 4
2.2
a .Wild curing conditions were 200 a C. for 3 minutes at 5 to 25 minutes at 5 to 25 tons platen pressures. addition of 0.5partper hundredparts resin of mineral acid. See footnote ( a ) , Table I I .
Table IV.
40
Drape Stifness (Length of Overhang, Inches) 3 . 7 dz 0 . 4 3.7 3.5
40
3.8
Elongation, % 48 ,
.
A uigorous cure was the same as abaue, with the
Nylon Randowebs Bonded with Vinyl Acetate Copolymers, Vigorous Curing Conditions"
3570 binder loading) Fabric Properties Break Strength, Lb./In./Oz./Sq. I'd. Tide Tide Perclene (70' F . ) (160" F . ) (70' F.) 7.3 1.9 2.4 6.4 2.0 2.6
(Applied from tetrahydrofuran,
Binder
llinh
Acrylate binder VAc-B.4-AAb 50 48.5 1 . 5 VA-EHA-A.4 55 5 43 1 5
2.45 1 73
Dry 9.1 9.7
1.04
9.7
Sre footnote ( b ) , Table III.
7.5
1.5
2.7
Etnk 30 35 40
Tongue tear, lb./ot./sq.yd. 1 2 1 6
1.5
Drape s t i f . , inches to bend 3.6 3.8
3.9
See footnote ( a ) , Table II.
VOL. 2
NO. 2
JUNE 1 9 6 3
111
Table V.
Nylon Randowebs Bonded with Vinyl Acetate or Ethyl Acrylate Copolymers, Vigorous Curing Conditions" (Applied from aqueous dispersion)
Binder in Fabric, yo
Binder
Acrylate binder 42 EA-AAb 43 98-2 VAC-BA-AA 42 50-48.5-1.5 VAC-EHA-~~A 39 52-46-2 See footnott ( b ) , Table III.
Dry 8.1 7.5
Brpak Strength, Lb./In./Ot./Yd.2 Tide Tide (70' F . ) (760' F . )
Drape Stiffness
5.8 4.7
2.5 2.0
2.0 2.4
Tear 1. o 1. o
6.8
5,s
1.9
2.6
1.6
2.9
5,9
4.7
1.8
1.8
1.7
3.0
* See footnote
3.0 3.5
( a ) , Table I I .
polymer gave fabrics with essentially equivalent properties to those obtained using the acrylate polymer as binder (Table IV). These data were obtained under the conditions of temperature and pressure previously mentioned (200' C./ 3 min./j tons), which were rather vigorous, to ensure that adequate curing had taken place. I n subsequent runs, the curing time could be shortened to as low as 30 seconds without harming fabric properties. Binder Application from Aqueous Dispersion. iYhen the binders were coagulated within the nylon Randoweb from aqueous dispersion with a freezing technique, rather than by coagulation from an organic solvent, similar values for the acrylate ester and the vinyl acetate polymers were again obtained, as shown in Table V. In this case, tivo additional observations may be made: When binder was applied from aqueous dispersion, the fabric strength and stiffness values with both the acrylate and the vinyl ester copolymer binders were somewhat lower (except for the 160' F. Tide value) than when those binders were coagulated from organic solvent. This appears to be a result of some of the polyether dispersing agent acting as a plasticizer and remaining with the binder in the coagulation step of the aqueous dispersion.
Table VI.
Perclene (70OF.)
T h e vinyl acetate polymers appear to be plasticized somewhat more efficiently than the polyacrylate system, a result which would also depend on the particular dispersing system formulation used in the polymerization.
Both points demonstrate the advantages of the solvent coagulation technique over a n emulsion coagulation technique for a comparative evaluation of the polymer used in the binder system. Fabric Durability. To assess the durability of the fabrics bonded with vinyl acetate polymers under hot-wet abrasive conditions, some preliminary Launderometer tests were set u p using the AATCC test I I I A conditions ( 7 1 , and repeated eleven times. As each cycle is reported to be equivalent to five domestic laundering cycles, this treatment could be considered as an exposure equivalent to 55 laundering cycles. This is really a colorfastness test under domestic laundering conditions. Although there is no generally accepted procedure for determining the launderability of a fabric by a n accelerated test, this test is frequently used as a guide to washability, though it does tend to overemphasize the abrasive deterioration of the fabric. The data (domestic) in Table V I indicate essentially no differences in launderability between vinyl
laundering Studies on Dacron Polyester Fiber Randowebs Bonded with Vinyl Acetate-Based Polymers
Binder (Cured)
Vinyl acetate copolymer "A" Acrylate binder Acrylate binder VAC-BA- AAS 49-49-2 VAc-DMB-E.4-.4A 55-22-22-1
VAC-BA-EA-AA
Binder Loading
Total Immersion Time, Hr.
Dry Break Strength of Fabric
Laundering Weight
70
Initial
L b. / I n . lot./Sq. Yd. Final
Diffei C I K ~
31 31
DOMESTIC LAUNDERING CONDITIONS~ 8.25 0.1 7.5 ... 8.1 8.25
7.5 8.0
...
35 35
COMMERCIAL LAUNDERISG CONDITIOKS~ 0 7.7 16 1.8 6.3 17
7.7 5.8
-0.5
LOSS,
0.1
...
34
17
1.2
6.4
7.0
-I-0.6
35
17
1.5
6.2
5.7
-0.5
57-27-20-1 Vinyl acetate copolymer "A"
35
16
3.4
6.7
6.9
+0.2
.4crylate binder VAC-BA- AA" 49-49-2
35 35
ABRASIVE .ACTIONd MINIMIZED 53 ... 53 0.5
34
53
0.9
35
53
1 .o
34
54
0.2
VAc-DBM-E A-AA
55-22-22-1 VAC-BA-E A-AA 52-27-20-1 Vinyl acetate copolymer "A"
The laundering technique used involred conThe laundering technique used involved cyclic operation and is equiualent to 55 domestic laundering cycles. See footnote tinuous operation, equivalent to greater than 30commercial cycles ( A A T C C Test I I I A conditions, but run continuousb at 160' F . for 17 hours). ( a ) , Table II. d The laundering technique used involved continuous operation with A A T C C Test 111.4, but with no steel balls in the containers and run continuously at 160" F. for 53 hours. a
112
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
acetate polymers and a n all-acrylate polymer under domestic laundering conditions. I n order to accentuate the durability differences between the binders, fabrics were submitted to a continuous 17-hour Launderometer treatment a t 160’ F. under AATCC test IIIA conditions. This test (using a polyacrylate binder), when run for 21 hours, was found by the Textile Fibers Department, Du Pont, to be equivalent to 40 commercial launderings under conditions of moderate severity. There are a number of so-called “commercial washings” ranging from the relatively mild washing of family colored goods to the drastic scouring given to rental uniforms. This treatment is intermediate in severity and corresponds to the wash given to rchite napery. Results show somewhat lower wet abrasion resistance-as indicated by the increased weight loss-for the vinyl acetate copolymers compared to the acrylates, but essentially equivalent hydrolytic resistance, as indicated by the maintained strength of the fabric (Table VI, “commercial” data). This view was substantiated by additional continuous runs, carried out as above, but without the steel balls being present in order to reduce the abrasive action. T h e results (Table VI, minimized abrasive data) after 53 hours’ total exposure indicate very small weight losses; slightly greater than for the all-acrylate polymer. Additional Binder-Fabric Relationships. Additional relationships observed between the vinyl acetate copolymer binder compositions and resulting fabric properties include the following: LVith a constant curing recipe, an increase in carboxyl content from 0.7 to 3.4 bvt. % in the 50-49.3-0.7 vinyl acetatebutyl acrylate-acrylic acid terpolymer increased the Perclene resistance, but also increased the drape stiffness of the fabric. The water (Tide) resistance went through a maximum a t about 1.7YG acrylic acid. Substitution of ethyl acrylate for butyl acrylate u p to 15 to 20% of the total polymer composition did not significantly change the fabric stiffness or strength properties. Changes of molecular weight in the inherent viscosity range of 0.75 to 2.3 had little effect on binder properties. As a result of these studies, a group of quadripolymers were prepared to give maximum economic advantage, and with properties essentially maintained. These are listed in Table VII.
Table VII. Binders Based on Vinyl Acetate with Equivalent Properties to Commercial Acrylate Binders Polymer Composition by Weight
V.4c-B.4-EA-.4Aa 54-24 5-20-1 V-4~-DBM-BA--4.4 54-22-22-2 VAC-DBF-EA-A.4 54.5-22-22-1 v.4~-DBXf-E.4-A.4 57-30-1 0-3 a
See footnote
(u),
5 5
Tuble II.
Discussion
4s indicated from the data in Table I, the sensitivity to water of various vinyl acetate-based polymer binders depends on the presence of hydrophilic polymeric materials in the binder composition and subsequently on the method of application of the binder to the fiber. Many of the commercial vinyl acetate polymer dispersions hitherto prepared and used for evaluation have been designed for adhesives or pigment binding applications. Such disper-
sions generally are based on polymers with relatively high moduli, and have contained high concentrations (3 to 6% based on resin) of hydrophilic, surface-active components such as poly(viny1 alcohol) or hydroxyethylcellulose. These dispersions, of course, are highly stable to permit wide latitude in further compounding with plasticizers, solvents, pigments, etc. -4s has been mentioned, ho\i ever, polymerizations of vinyl acetate carried out in the presence of poly(viny1 alcohols) lead to mixtures of graft copolymers and vinyl acetate homopol) mers (77), and these result in relatively water-sensitive products compared Ivith the pure homopolymers. Furthermore, attempts to develop water, high temperature, and solvent resistance for such polymer blends by treatment with formaldeh>de donors have been quite inefficient, probably because of the heterogeneous distribution of the h!droxyl grouos. On rhe other hand, preparation of the vinyl acetate copolymer binders under conditions which did not result in grafting of h>drophilic components led to bonded fabrics which, when properly cured, had properties that were comparable to the acrylate bonded fabrics in dry strength, wet strength, and tear strength a t equivalent drape stiffness. Resistance to dry cleaning solvents and hot-wet abrasion resistance may be slightly lower for the vinyl acetate copolymers. a t least with this curing recipe; but both the acrylate ester and the vinyl ester binders appear to be well Lvithin the satisfactory range for fabrics subjected to commercial \cashes. I n the binder area, economic considerations are very important. The comonomers chosen for the binder candidates listed in Table VI1 were those which would furnish the desired internal plasticization with maintenance of other fabric properties, and a t the lowest possible raw material cost. Based on present prices of the monomers, and with polymerization processes being very similar to those for the acrylates. these comonomers should permit a significant cost advanrage for \ inyl aceta te-based copolymers over the all-acrylate polymers. Acknowledgment
LVe wish to expresq our appreciation to Z. hfandel, ‘Textile Fibers Department, for the initial work on the curing formulations, to h l . Fields, J. A. Reeder, and \%’.L. Kohlhase. Electrochemicals Department. for their contributions to this uork, and to B. S. Brown of the Engineering Service Division, E. I. du Pont de Semours 8: Co., Inc., for hi. statistical assistance. Literature Cited
(1) .4merican .4ssociation of Textile Chemists and Colorists, Technical Manual, pp. 102-3, Howes Publishing Co., Inc., NewYork, 1959. (2) Backer, S., Petterson, D. R., Textile Res. J . 30, 704-7 (1960). (3) Coke, C. E., Chem. Ind. (London) 1958,pp. 1569-76. (4) Drelich, .4. H. (to Chicopee Manufacturing Co.), U. S. Patents 2,880,111-13 (March 31, 1959). (5) Hartley, F. D., J . Polymer Sci.34, 397-417 (1959). (6) Hentschel, R. A. A , , Tuppi 42, 979-82 (1959). (7) Ibid., 44, 22-6 (1961). (8) Homier, P. .4., A m . Dyestuff Reptr. 49, 16-17 (1960). (9) Moffett, R. P., Mod. Textiles Mag. 37, No. 10, 62-5 (1956). (10) Nicely, D. C., A m . Dyestuff Reptr. 49, 17-19 (1960). (11) Okamura, S.: Motoyama, T., Yamashita: T., Chern. High Poiyniers (Tokyo) 15, 165-74 (1958). (12) Taylor, J. T., A m . Dyestuff Reptr. 46, 437-42 (1957). (13) Ibid., 48, KO.5, 49-53 (1959). RECEIVED for December 7, 1962 ACCEPTED April 1, 1963 Division of Cellulose Chemistry, 142nd Meeting, ACS, Atlantic City, N. J., September 1962.
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