US3814676A

US3814676A - Radiation process of preparing grafted elastomeric fibers wherein post-decrystallization is employed

Info

Publication number: US3814676A
Application number: US00187505A
Authority: US
Inventors: J Williams; V Stannett
Original assignee: JP Stevens and Co Inc
Current assignee: JP Stevens and Co Inc
Priority date: 1971-10-07
Filing date: 1971-10-07
Publication date: 1974-06-04
Anticipated expiration: 1991-06-04

Abstract

CELLULOSE-CONTANING FIBROUS MATERIALS SUCH AS RAYON YARN ARE CONVERTED INTO ELASTIC MATERIALS BY A PROCESS IN WHICB THE FIBROUS MATERIALS ARE IRRADIATED, AN ACRYLATE MONOMER IS GRAFT COPOLYMERIZED ONTO THE IRRADIATED MATERIAL AND THE PRODUCT OF THE GRAFTING PROCESS IS TREATED WITH A DECRYSTALLIZING AGENT. THE ELASTIC PRODUCT OBTAINED POSSESSES GOOD EXTENSIBILITY AND ELASTIC RECOVERY AND CAN BE USED IN PALCE OF FIBROUS RUBBER IN THE PREPARATION OF ELASTIC PRODUCTS.

Description

United States Patent 3,814,676 RADIATION PROCESS OF PREPARING G RAFTED ELASTOMERIC FIBERS WHEREIN POST-DE- CRYSTALLIZATION IS EMPLOYED Joel L. Williams, Cary, and Vivian T. Stannett, Raleigh, N.*C., assignors to J. P. Stevens & Co., Inc., New York, N.Y. No Drawing. Filed Oct. 7, 1971, Ser. No. 187,505 Int. Cl. Blllj 1/10, N12 US. Cl. 204-15912 6 Claims ABSTRACT OF THE DISCLOSURE Cellulose-containing fibrous materials such as rayon yarn are converted into elastic materials by a process in which the fibrous materials are irradiated, an acrylate monomer is graft copolymerized onto the irradiated material and the product of the grafting process is treated with a decrystallizing agent. The elastic product obtained possesses good extensibility and elastic recovery and can be used in place of fibrous rubber in the preparation of elastic products.

The present invention relates to a method of imparting elastic properties to fibrous cellulose-containing materials by grafting acrylate compounds thereon.

Heretofore, acrylate monomers such as ethyl acrylate have been co-polymerized onto rayon for the purpose of producing elastic fibers, However, such efforts have either been unsuccessful or have achieved elasticity only after very large amounts of ethyl acrylate have been grafted onto the rayon.

An article by Nakamura et a1. entitled, Elastomers Based on Cellulose Fibers, Journal of Polymer Science, Part C, Number 23, pp. 629-645, 1968, discloses grafting ethyl acrylate onto rayon fibers using ceric ion initiation and indicates that high graft levels are required to obtain elasticity. The use of a pretreatment with a zinc chloride decrystallizing agent increases the elasticity at a given graft level to some degree, but still an extent of grafting of over 1000 percent was required to obtain rubber-like behaviour. In a subsequent article by Nakamura et al., entitled Rheological Properties of Elastomers Based on Cellulose Fibers, Polymer Preprints, Vol. 11, Number 1, February 1970, Division of Polymer Chemistry, A.C.S., work is described wherein rayon yarn is irradiated prior to grafting ethyl acrylate thereon. This process increases the elasticity of the grafted product but still, even at high irradiation dosages, a graft level of about 300 percent was required to obtain an elastic fiber.

In accordance with the present invention an elastic fibrous material is provided by grafting an acrylate compound onto a cellulose-containing fibrous material using a procedure by which the elasticity can be obtained when the extent of grafting is as low as 50 percent by weight based on the weight of the fibrous material. In this process the cellulose-containing fibrous material is irradiated, there is grafted onto the irradiated material an acrylate compound of the formula where R is hydrogen or methyl and R is alkyl of 1 to 6 carbon atoms;

and the product of the grafting step is treated with a decrystallizing agent for the cellulose-containing fibrous material.

The irradiation treatment ise carried out by exposing the cellulose-containing fibrous material to high energy irradiation such as gamma rays from cobalt-60. The dose 3,814,676 Patented June 4, 1974 ice of irradiation given to the cellulose-containing fibrous material should be from about 0.1 to megarads with a dose of 0.2 to 50 megarads being preferred. It is preferable to carry out the irradiation while maintaining the cellulose-containing fibrous material under vacuum, but irradiation can be carried out under atmospheric conditions. The irradiation decreases the degree of polymerization of the cellulose in the fibrous material with increasing irradiation dosages giving greater depolymerization and an increase in the elasticity of the final product. The dose should be limited to about 100 megarads to prevent excessive degradation of the cellulose. The irradiation forms radicals in the cellulose which are capable of initiating grafting in the subsequent grafting step.

Grafting is carried out using an aqueous emulsion of an acrylate compound of the above given formula. Preferably the emulsion contains about 1 to 60 percent by weight of the acrylate compound and 40 to 99 percent by weight of water. Other additives may be present such as up to 5 percent by weight of a dispersing or emulsifying agent. Illustrative of suitable acrylate compounds are methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate and the corresponding methacrylates. Mixtures of these compounds can also be employed. To obtain elastic properties, the extent of grafting should be equal to at least 50 percent, preferably 100 percent, by weight based on the weight of the original cellulose-containing fibrous material.

Following the grafting step, the product is treated with a decrystallizing agent for the cellulosic material. Illustrative of decrystallizing agents are zinc chloride, cupriethylene diamine, cupritetramine hydroxide, concentrated liquid ammonia, lithium hydroxide, benzyltrimethylammonium hydroxide, ethylamine and ethylenediamine. Where the decrystallizing agent is a solid material it can be used in a concentrated solution in a solvent such as water.

In order to obtain elastic material at low levels of grafting, it is essential that the treatment with the decrystallizing agent be carried out after grafting. When the decrystallizing agent is used prior to grafting, the cellulose recrystallizes during the grafting step and little improvement in elasticity is obtained. It is believed that the large increase in elasticity obtained by treatment after grafting (post-decrystallization) is a result of the grafted material preventing or interfering with recrystallization. Although the best results are obtained with a fibrous cellulose-com taining material which has been irradiated, the use of the above-described post-decrystallization is not limited to irradiated material. When a high extent of grafting is desirable or permissible, post-decrystallization can be used to give improved results where the cellulose-containing material has not been irradiated and the grafting of the acrylate compound has been initiated by other means such as chemical means, e.g., ceric ion initiation.

'Ihe cellulose-containing fibrous material can be in the form of fibers, filaments or yarns, or fabrics made therefrom. The cellulose can be from any source, including such natural sources as seed fibers such as cotton; bast fibers such as flax (linen); ramie, jute and hemp, as well as regenerated cellulose such as rayon where wood may serve as the source of cellulose.

The products obtained by the present invention possess good extensibility as measured by elongation at break and good elastic recovery. The products can be used in place of fibrous rubber in the preparation of elastic products.

The following examples are given to further illustrate the invention, but it is understood that the invention is not to be limited in any way by the details described herein.

3 4 EXAMPLE 1 Samples of various types of rayon yarn weighing 100 Percent brealnng elongation milligrams each were wound on three-prong glass tares Percent gf i g f 70% and placed into glass ampoules. Subsequently, Itlhe am- Sample graft; z i n cuene, ZnClg oules were evacuated at lmm. Hg. for 16 ours at 5 55 C. and sealed under vacuum. The samples were then gfi t fiigfifffijjjjjjj: gig :18 288 gg irradiated in a cobalt 60 facility at dose rates of 0.1-0.2 megarads per hour at 25 C. Following irradiation degassed emulsions of 55 millimols ethyl acrylate (EA) EXAMPLE 5 and 19.0 ml. of an aqueous 5% solution of an alkyl aryl hi example illustrates the use of pestdeerys- Polyether aieohol emulsifier were added to each p tallization to improve elastic properties where the cellu- The Samples in Contact with the grafting Solution were lose-containing material Was not irradiated. Samples of Placed into a water bath maintained at and grafting a continuous filament viscose rayon yarn (150 denier, was allowed to proceed for the times indicated with slight 40 fil id l), wound without tension on a threeagitetion- Following the grafting Period the Samples were pronged glass bobbin, were placed in a test tube containwashed in at least three changes of water and then soxhlet i th ifi d tit of C (NH (NO= 6H O extracted with acetone for 8 hours to assure complete i i i 10 illi l HNO d enough water t give removal of homopolymers- 100 gms. of the final grafting solution. The system, main- Post-decrystallization was carried out by exposing the m d at 35 C, was purged with N fo 30 min, nd grafted yarn to 70% aqueous ZnCl at 60 C. for 30 during the last ten minutes of this time, ethyl acrylate, m t s followed y thorough washing with Water and contained in a burette inserted in the system, was simuldrying in a Vacuum oven at Cupriethyiene diamine taneously purged. The ethyl acrylate was added to the for minutes at foiiowed y water reaction and grafting was continued for the time specified washing and drying was also used in parallel p y with the bubbling of nitrogen being maintained for the tallizatiou experiment 25 entire grafting time. Upon removal of the samples from The Peieeht graft, based on initial Sample weight, was the graft solution they were washed several times with calculated and the breaking extensions determined on an tap water, then the acetone to remove h b of h 1115mm table model tester Sing a crosshead Speed of homopolymer. Soxhlet extraction of the rewound samples 2 in./mkn. at 21 C. and 65% RH.

Percent breaking elongation Dose rate Grafting Before Dose (Mrads/ time Percent deerystah 70% Rayon t (Mrads) hr. (hrs) graft lization Cuene. ZnCl Sifiihififiiifififih hfififiihittai" 2:8 3:3 81% 15% 233 238 i 18 Dnllsfanln k 11. 4 O. 1 fi .i fff filament 3,? ii; 1015 530 1410 540 500 All skin 9. 7 0. 2 7. 0 179 12. 0 480 300 EXAMPLE 2 with acetone was then continued until constant dry sample weights were obtained. cotton yam was grafied a g i aslrayO-n Post-decrystallization of grafted yarns was carried out m Example 1 except usmg 2 In} 5 at i ate m by exposing the samples wound on glass bobbins to 60% 28 ml. of the 5% aqueous solution of emulsifying agent a Z C1 1 t C f 20 Th 1 25 C. Also the total dose was 4.7 Mrads at a 0.1 queens n 2 i u Ion a or e es at f 2 h were washed with water, then with 0.1% acetlc acid, and Mrads/hour rate The grafting Period was or 4 ours finally with water and dried under reduced pressure over Sample Cotton. a mixture of CaSO /CaCl Percent graft 192. Percent graft, and physical properties were found as Percent breaking elongation: in Example 1.

Before decrystallization P t W t Cuene. 0 ercen I1 ima 8 7 ZnCl 400. iii-$3 ehngatmn Ce late, Time, Before Post EXAMPLE 3 Sample riib l s b l s i'ii s g r eit fi z a ti ii li z iiii h A sterilized cotton gauze pad was grafted in a similar B 0.5 31 so 590 47.6 79.2 fashion as rayon in Example 1 except using 111 millimols f g ff i 90 415 22-? 2g; of ethyl acrylate and 19 ml. of the 5% aqueous solution i of emulsifying agent- Also: the P dose 42 Mrads It will be apparent that many modifications and variaat a 0.1 Mrad/hour rate. Grafting was carried out for tions can be fl t d Without departing f the scope hours at of the novel concepts of the present invention, and the Samp1e Cotton gauze pad illustrative details disclosed are not to be construed as Percent ft 79 Imposing undue limitations on the invention. Percent breaking elongation: 5 What is claimed is:

B f deerystallization 35 1. In a process for imparting elastic properties to a Queue 4 cellulose-containing fibrous material by subjecting said 7 ZhClz 400 fibrous material to high energy radiation and graft copolymerizing onto said irradiated material at least one EXAMPLE 4 acrylate compound of the formula: A cellophane film (regenerated cellulose) of 1.5 mils R o in thickness and a Whatman Filter Paper No. 2. (cellu- CHpiJ-ii-Oltr lose fiber mat) were treated in a similar fashion as exwhere ample 1 except at a total dose of 3.2 Mrads and a grafting R is hydrogen or methyl and period of one hour.

R is alkyl of 1 to 6 carbon atom the improvement wherein the product obtained after said grafting is treated with a decrystallizing agent for cellulose selected from the group consisting of zinc chloride, cupriethylene diamine, cupritetramine hydroxide, concentrated liquid ammonia, lithium hydroxide, benzyltrimethylammonium hydroxide, ethylamine and ethylenediamine, said process requiring an irradiation dose of about 0.1 to 100 megarads and an amount of acrylate compound copolymerized onto said irradiated material equal to at least 50% by weight based on the weight of said irradiated material.

2. A process as claimed in claim 1 wherein said acrylate compound is ethyl acrylate.

3. A process as claimed in claim 1 wherein said cellulose-containing fibrous material is made of rayon.

4. A process as claimed in claim 1 wherein said cellulose-containing fibrous material is made of cotton.

5. A process as claimed in claim 1 wherein said decrystallizing agent is selected from the group consisting o zinc chloride and cupriethylene diamine.

6. A process as claimed in claim 1 wherein said cellulose-containing material is subjected to an irradiation dose of about 0.2 to megarads and the amount of acrylate compound graft copolymerized onto the irradiated material is equal to at least by weight based on the weight of the irradiated material.

References Cited Nakamura el al., Cellulose Graft Copolymers, I. of Applied Polymer Science, vol. 15, pp. 391-401 (1971).

Nanamura et a1, Elastomers Based on Cellulose Fibers, J. of Polymer Science, Part C, No. 23, pp. 629-645 (1968).

JOHN C. BLEUTGE, Primary Examiner R. B. TURER, Assistant Examiner US. Cl. X.R.

8-l 16 R, 129; 260-17 A, 17.4 GC