US2336265A - Coated fabric - Google Patents

Description

Patented Dec. 7, 1943 COATED FABRIC Robert L. Lester, N ewburgh, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, De1., a corporation of Delaware No Drawing. Application August 20, 1941, 'Serial No. 407,608

3 Claims. (01.117-166) This invention relates to the production of coated fabrics, and more particularly to the production of shade cloth for window shades and the like, having improved properties.

Window shade cloth comprising a textile fabric coated with acellulose nitrate composition is well known in the art of coated fabrics and has been developed to a point where it is considered generally satisfactory. However, there is need for improvement where the shade cloth is subjected to sunlight exposure over a long period of time. A serious objection of the present-day material is technically referred to as tendering. By tendering is meant that a shade cloth loses after prolonged exposure to sunlight much of its original tensile strength. A further objection of the prior art material is a lack of color stability, particularly in the case of white and other light colored translucent shade cloth materials.

It is well known that zinc oxide is an excellent filter for ultra violet light and, for this reason, it has been used quite extensively in pyroxylin ments have been reduced to less than the wave length of ultra violet light which is less than 4,000 angstroms which corresponds to .4 micron. In a systematic study of the effect of the taining such pigments, it was found thatparticles coatings for window shade material to filter ultra violet light which is known to have a deleterious v effect on nitrocellulose. By the use of zinc oxide in pyroxylln coatings for window shade material definite improvements have been made with respect to tendering. However, there is need for further improvement since the grades of zinc oxide normally used do not give completely satisfactory results withres'pect to tendering andcolor stability.

An object of the present invention is the provision of an improved shade cloth material. A

terialhaving great resistance to color change,

particularly in the case of white and other light colored shade'cloth'material, when exposed to sunlight over a prolonged period.

having a greater diameter than .4 micron or in the case of acicularshaped particles, those having a width greater than .4 micron, deteriorated less than similar material containingv zinc oxide particles less than .4 micron under simultaneeous conditions of exposure. It was also discovered that there was greater color stability in the case of the material employing the larger particles of zinc oxide.

An accelerated test for window shade material is obtained by exposing the material at Hialeah, Florida, in a closed box with a glass cover for a period of 40 weeks. The material is positioned in the box four inches from the glass at an angle of 45 and facing south. The surface temperature of the window shade material when exposed posed to'in actual service.

a The objects of this invention are accomplished by coatingjeach side or a textile fabric base material with a liquid coating composition comprising a solution of nitrocellulose, a plasticizer, and pigment. At least 20% of the total pigment in the coating composition consists of zincoxide parti'cleathe size of which is greater than .4

, micron in any one'direction.

gloss of the coating. The particle size ot'pigunder these conditions often reaches 200 F. due to lack of circulation of air inside the exposure box. This temperature is far in excess of any temperature the windowshade material is ex- The exposure in Florido. as described corresponds to approximately 10 years of service under normal conditions.

The following examples are given to illustrate specific embodiments of the invention, although it is to be understood that the invention is in no way limited to these particular examples.

To a suitable sheeting, such as one running 4.95 yards per pound at a' width of 37 /2 inches, and having a thread count of 68 x 72, is applied by means of a doctor knife on each side a total of 0.3 to 0.8 ounce, dry weight, per square yard, which corresponds to a total of 0.6 to 1.6 ounces per square yard on both sides of a suitable liquid coating composition. After the volatile solvents of the coating composition are expelled by pass .fl m bontain'jng the larger particles did the fabric corresponds to 1.2 to 3.2 ounces per square yard.

cial use and material which deteriorates less than 35% upon 40 weeks of Florida exposure is considered satisfactory for commercial use and is acceptable to the trade in general.

In the case of the so-called opaque material the drycoating composition may be as follows:

Parts by'weight Cellulose nitrate 43.0-25.0 Pigment 45.0-56. Dibutyl phthalate 12.0-18.7

The method of preparing the above compositions which comprises dissolving. the cellulose nitrate in organic solvents to form a solution andgrinding the pigment'in the plasticizer before blending with the'solution is well known in the art and forms no part of the present invention and a detailed description of such method does not appear to be necessary.

Duplicate samples of white translucent window shade material were made employing nodular shaped zinc oxide as the total pigment content. In one case the diameter'of the zinc oxide pigment particles corresponded to 1.0 to 1.5 microns and in' the other case the diameter of the 'zinc oxide pigment particles corresponded to .25 to .30micron. Both materials were exposed slmultaneously at Hialeah, Florida, under glass and four inches from the glass facing. south at an angle of 45 fora period of 40 weeks. The tensile strength of each material was measured before exposure, at the end of 20 weeks exposure, and at the end of 40 weeks exposure.

' The following table indicates the results of deterioration of tensile strength of window shade 55 material employing nodular shaped zinc oxide In the case oftranslucent window shade vma- The fqlldwing tablelmdicatfas n' terial the dry coating composition may be as fol taimfd wlflh aclcula'l' Shaped Zmc oxlde wf lows. particles incorporated in the coating composltlon.

.' Inasmuch as acicular zinc oxide particles are not Parts y weight available in widths less than .4 micron, the

Cellulose n t 110 nodular shaped zinc oxide having a diameter Pigmen V d of .25 to .30 micron -was'employed as a control yl p h l t 2B.231. 4 f th following t Initial tensile V Tensile strength after weeks ,Tensile strength after 40 weeks strength 4 ,Florida exposure Florida exposure Particular size-oi ziil c oxide particles in mg Per cent Per cent W- n F- W. F. W. and F. deterlora- W. F. W. and F. deterioration tion Nodular (diameter):

.25 to .30 micron 68 46 114 57 35 92 19 4a 19 67 41 Acicular Width .54 micron, length 3.2 mlcrons 73 46 119 -7 4 3 1 3 37 00 a 1 Width .43 micron, length 3.2 microns.-- 69 46 115 7 103 v 6 2 3 g 5 Width .43 micron. length 3.2 microns--. 67 42 l 109 2 40 102 6 l 3 3 99 9 At the end of the 40 weeks exposure in Florida,

the'original tensile strength-of the window shade material containing the nodular shaped particles ranging in diameter from .25v to .30 micron had deteriorated 41%; whereas the original tensile strength of the material containing the larger acicular shaped particles only deteriorated 9% to' 16%. The material containing the smaller particles of zinc oxide developed a yellow cast during-the exposure period; whereas the material containing the larger particlesdid not undergo any color change. I

These results are surprising since in the paint and lacquer field the tendency is. to increase-the hidingpower by decreasing the size of the pig- 0' ment particles. Therefore, one skilled in the art who was confronted with the problem of producing 'a shade cloth material capable of filtering ultra violet light to prevent tendering would undoubtedly resort to thesmaller pigment particles to accomplish increased hiding power.

It is probable that the yellowcolorwhich develops in the. case of material containing the smaller particles of zinc oxide results from the decomposition of the nitrocellulose binder rather than any color change of the pigment.

In order to make a wide range of colors in window shade material it is necessary to blend 'thezinc oxide pigments with various colored pigments, such as carbon black, bone black,

chrome green, chrome yellow, ultramarine blue, .iron oxide and various colored lakes.

as the total pigment content:

The whitejmaterial containing the smaller zinc xi i ment particles had definitely yellowed at the endjofthe- 40 weeks exposure and the simnot i9;ny p tt'antial yellowing during the 1 same per-loch,

Material whi'ch deteriorates more than 315%311' fig i fle kst 'e'ngth pon 40 weeks of- Florida ex- 1 him] tensile Tensile Smngth-"m'er 0 Weeks Tensile strength after 40 weeks Qstrcnsth F r d exposum Florida exposure Diameter-oi nodular zlncox ide particles in V f I I coating 7 h 1 Percent Percent W F. W. and F. W. F. W. and F. deteriora- W. F. 'W.and F. deteriora- 1.1---1. 61 4e no 52 1 m 39 19 L 58 s 47 l. Mgfifii 7o 49 119 67 -41 @103 A 9 56 32 8S 7 crue'if the largeparticle size zinc oxide (greater than ;.4 .micron-'m all dimensions) is present in '70 amounts 'less than-20% o f theg'total pigment content of thedry coating composition. j The may vary between 20% Pigment'content. o

o low. r thetotal The. advantages of this invention do Inot ac The compositions given in the examples are merely illustrative. Any well known softener may be used in the composition such as castor oil, blown cottonseed oil, blown rapeseed oil, or the like, but it is preferred to employ a so-called solvent softener, such as dibutyl phthaiate, dibutyl tartrate, etc., and resinous plasticlzer since the solvent softeners tend to reduce the tendency of the shade cloth to curl as is disclosed in U. S. Patent 2,033,170.

To obtain the improved results of the present invention, it has been found that zinc oxide, either the pure or leaded varieties, must be employed. The zinc oxide pigment may be either of acicular or nodular shape. In the case of acicular shaped particles of zinc oxide, the smallest dimension (width) of the particle should not be less than .4 micron.

-'The proportions given in the example are merely illustrative and may be varied over a wide range as will be readily apparent to those skilled in the art, the proportions being governed by the desired degree of translucency. In .the case of equal weights of coating on the winproduced in accordance with the present invention is the resistance of the material to tendering upon prolonged exposure to sunlight and heat, and a much greater life than window shade material produced in accordance with the prior art. A further advantage is resistance to yellowing upon prolonged exposure to sunlight.

The present invention has been described with respect to shade cloth, but it will be apparent that the invention applies to other types of cellulose derivative coated fabrics and the term "window shade material" as used herein and in the appended claims is intended to include cellulose ester coated fabrics in general having properties'simiiar to shade cloth, such as, e..g., sign cloth used in buses, trolley cars, etc.,as illuminated signs.

It is apparent that many widely different emposed thereon consisting essentially of cellulose nitrate, a plasticizer, and pigment, at least 20% of the said pigment comprising zinc oxidehaving a particle size greater than .4 micron and less than about 3.2 microns in any one direction.

2. A window shade materialresistant to tendering and color change comprising a fabric parts, at least 20% of total pigment content consisting of zinc oxide having a particle size greater than .4 micron and less than about 3.2 microns in any one direction.

ROBERT L. LESTER.