US3843389A - Process for impregnating webs with polymer solutions - Google Patents

Abstract

1. A PROCESS FOR THE UNIFORM IMPREGNATION OF A FIBROUS MAT WITH A POLYMER SOLUTION COMPRISING THE STEPS OF PASSING A FIBROUS MAT HAVING A SURFACE THROUGH A SUCCESSION OF SUBSTANTIALLY IDENTICAL GAPS EACH DEFINED BETWEEN PAIRS OF ROLLERS, COATING SAID ROLLERS UNIFORMLY AND CONSTANTLY WITH SAID POLYMER SOLUTION, THE GAPS BETWEEN SAID ROLLERS BEING SUCH THAT SAID FIBROUS MAT IS NOT SUBJECTED TO COMPRESSION THEREBETWEEN BY THE ROLLERS PER SE, MAINTAINING THE CLEARANCE OF SAID GAPS EQUAL TO OR GREATER THAN THE THICKNESS OF SAID MAT, DRIVING EACH OF SAID COATED ROLLERS IN THE SAME DIRECTION AS THE ADVANCING DIRECTION OF THE FIBROUS MAT AT A SPEED AT LEAST TWO TIMES FASTER THAN THE SPEED AT WHICH SAID FIBROUS MAT ADVANCES, AND TRANSPORTING A UNIFORM STREAM OF SAID POLYMER SOLUTION TO SAID MAT ON ITS SURFACE TO IMPREGNATE SAID MAT.

Description

Oct 11 11 1974 mm ENOMOTO PROCESS FOR IMPREGNATING WEBB WITH POLYMER SOLUTIONS QriginaIFiled Aug. 4, 1969 FlG- -i United States Patent 3,843,389 PRQCESS FOR IMPREGNATING WEBS WITH PGLYMER SOLUTIONS Yuya Euomoto, Kurashiki, Japan, assignor to Kurashiki Rayon (30., Ltd, Kurashiki, Japan Continuation of application Ser. No. 847,359, Aug. 4, 1969, which is a continuation-in-part of application Ser. No. 539,843, Apr. 4, 1966, both now abandoned. This application Mar. 8, 1972, Ser. No. 232,982

Int. Cl. BilSc 9/04; B44d 1/02 U.. Cl. 1ll7--68 2 Claims ABSTRACT BF THE DISCLOSURE A process is disclosed for impregnating a polymer solution into a fibrous mat by using a succession of gaps between pairs of rollers which are wide enough apart to prevent compression of the fibrous mat. 'Ihe rollers are driven in the same direction as the advancing direction of the fibrous mat at a speed at least twice as fast as the advancing speed of the mat. The use of such a speed permits 100% impregnation.

This application is a continuation of Ser. No. 847,359, filed Aug. 4, 1969 and now abandoned, which in turn is a continuation-in-part of application Ser. No. 539,843, filed Apr. 4, 1966 and now abandoned.

The present invention relates to a novel process for impregnating fibrous mats such as webs, non-woven cloths formed of fibrous materials and felts with polymer solutions.

Usually, for impregnation of such materials with polymer solutions, either a stationary process or dip process is employed. The former consists of floating a fibrous mat on the surface of a polymer solution, whereby the solution can fully permeate through the inside of the mass with relative uniformity owing to capillary ascending action of the solution. However, the higher the viscosity of the polymer solution, the longer the time required for thoroughly impregnating a fibrous mat with the solution, and sometimes it is highly difiicult to attain thorough impregnation. The latter is a process for dipping a fibrous mat in a polymer solution, in many cases with an additional step of compression with rollers, whereby relatively thorough impregnation is effected. However, this often results in application of unnecessary compressive force upon the fibrous mat to effect adversely the properties of the material after the process. Further, as the viscosity of the polymer solution is increased the number of pores formed in the fibrous mat is increased due to accumulation of bubbles in the solution and ununiform impregnation.

It is an object of the present invention to provide a novel process which overcomes the disadvantages of known processes.

The present invention consists in a process for the impregnation of a fibrous mat with a polymer solution, in which a fibrous mat is passed between a pair of parallel rollers, the gap between which being such that the fibrous mat is not subjected to compression therebetween, at least one of said rollers being driven in the same direction as that the fibrous mat advances at a speed faster than the fibrous mat advances and transporting on its surface a uniform stream of the said polymer solution to the surface of the said mat.

The invention is further illustrated with reference to the accompanying drawings, in which:

FIG. 1 is a side view illustrating the basic conception of the present invention; and

FIG. 2 is a side view of a preferred embodiment of the invention corresponding to FIG. 1.

Patented Get. 22, 1974 Basically the process of the invention comprises adjusting the clearance between a pair of rollers to a value equal to or greater than the thickness of a fibrous mat, revolving the rollers 2, 2', in the same direction as the advancing direction of the fibrous mat ll shown in FIG. 1, supplying a predetermined amount of a polymer solution 3, 3' uniformly and constantly on the rollers, and thus impregnating the fibrous mat with the polymer solution. The advancing direction of the fibrous mat is necessarily the same as the running direction of the rollers 2, 2'. It is preferred to revolve the roller at a speed 2 times or more faster than that of the advancing fibrous mat. In FIG. 1, numerals 4, 4' designate drainers for controlling the supply of polymer solution. In the practical application of the invention, the number of rollers is not confined to a pair but a multi-stage roller arrangement as shown in FIG. 2 may be used to effect repetition of impregnation depending on the required amount of impregnant. It is preferred to use at least four-stage roller arrangement. Control of the amount of the solution impregnating the fibrous mat can be optionally varied by adjusting the amount of the polymer solution to be supplied to each roller, because there is a certain relationship among the amount of the polymer solution to be supplied, the number of impregnation cycles employed, and the amount to be actually impregnated, with respect to the impregnation tendency of the polymer solution. Further, in order to carry out the maximum impregnation of a fibrous mat, the clearance between the rollers must be greater than the thickness of the fibrous mat, because if the roller clearance is less than the thickness of mat, a sufficient impregnation effect cannot be achieved. Moreover, according to the impregnation process of the invention, the temperature of polymer solution can be controlled easily through control of the roller temperatures with a heating medium.

While in the impregnation process above described a fibrous mat is impregnated with a polymer solution fed simultaneously from a pair of opposite rollers (2, 2' in FIG. 1), it is also possible to supply the polymer solution to only one of the rollers and to impregnate the fibrous mat from only one side thereof. In the latter case, the time required to impregnate thoroughly the fibrous mat with the polymer solution is of course prolonged, and the necessary number of roller stages is increased. However, depending on the intended purpose of the mat, it is sometimes necessary to impregnate a fibrous mat partially with a polymer solution or to keep the mat from being fully impregnated. In such case, the impregnation from only one side of the mat is effective.

The process of the invention can be carried out even when the solution to be used for the impregnation contains minute pigment particles, fine power of synthetic or natural high molecular weight polymer, or fine powder of organic or inorganic substance, which is insoluble in the solvent, in a dispersed state.

Now the impregnation process of the invention is illustrated by the following examples.

Example I A needle-punched web formed of mixed-spun fibres of nylon-6 and polystyrene at a ratio of 45:55 (which web weighed 350 g./m. and had a specific gravity of 0.20) was impregnated with a solution of polyurethane in dimethyl formamide by the use of a four-stage roller unit in accordance with the impregnation process of the invention. The results as classified by the viscosity of polymer could accomplish thorough impregnation in a short time regardless of the viscosity of the solution used.

The polyurethane used was prepared by reacting polybutylene adipate glycol, diphenyl methane diisocyanate and 1.4-butylene glycol. 5

TABLE 1 Type of polymer solution (percent) Gone. 22%, 25

Gone. 22%, 46

Gone. 22%, 86 Gone. 26%, 350

i The time required represents the period during which the web passed through the four states of rollers, hence depending on the velocity of the web. In this case, the velocity at which the web passed was 3 m./min.

3 The time required represents the period during which the web was floated on the surface of a polymer solution and was impregnated completely across the entire section.

Example 2 Woollen felt (weighing 320 g./m. with a specific g5 gravity of 0.25) was impregnated with a solution of the 3 This represents the maximum amount of impregnant of the web, calculated by the formula: Magnification of impregnation= (weight of web after impregnation) (weight of web before impregnation) (weight of web before impregnation) The viscosity is the value determlncd at 30 C. 5 The magnification ofimpregnation after dipping for one hour was 3.9.

tionary process. In Table 3, there are shown the comparative results in terms of the periods of time required and magnifications of impregnation.

TABLE 3 Type of polymer solution Gone. 22% Gone. 22%, Gone. 26%, Process of impregnation Item measured 25 poises 86 poises 630 poises Remarks Time required Within 1 min Within 1 min Within 1 min. Process of the invention ig of impregnation 4] g 6 i H Roller temp.. 30 C.

- iine required 5 min 0 min ver r. o

p pwcess of impregnation U 4.6 i i o p y SOL 30 *The magnification of impregnation alter dipping for one hour was 3.0.

polyurethane described in Example 1 in dimethyl formamide by the use of a four-stage roller unit in accordance with the invention, and the results were compared with those attained by the conventional dip process which combined with compression with rollers. The process of the invention permitted the felt to be impregnated uniformly What is claimed is: ii. A process for the uniform impregnation of a fibrous mat with a polymer solution comprising the steps of passing a fibrous mat having a surface through a succession of substantially identical gaps each defined between pairs of rollers,

without bubbles, whereas the dip process caused accumulacoating said rollers uniformly and constantly with said tion of bubbles in the impregnating solution, which in polymer solution, the gaps between said rollers being turn increased the number of pores in the felt, thus keep such that said fibrous mat is not subjected to coming the magnification of impregnation at a low level. I pression therebetween by the rollers per se,

The results are shown in Table 2. maintaining the clearance of said gaps equal to or TABLE 2 Type of polymer solution Gone. 22% Gone. 22% Gone. 26%

Process of impregnation 25 poises 8G poises 350 poises Remarks Magnification of impregnation by the process of the invention 4. 0 4. 0 4. 0 Roller temp; 30 C. Magnification of impregnation by the dip process 3. 8 3.8 3. 6 Temp. of polymer so1.: 30 C.

Example 3 Non-woven cloth of 6-nylon fibres (weighing 400 g./m. with a specific gravity of 0.21) was impregnated with a greater than the thickness of said mat, driving each of said coated rollers in the same direction as the advancing direction of the fibrous mat at a 5 6 speed at least two times faster than the speed at 2,119,480 5/1938 Codwise 117-111 F which said fibrous mat advances, and 2,396,946 3/1946 Grupe 118-249 transporting a uniform stream of said polymer solution 2,582,407 11/ 1952 Barrett et al 117-111 F to said mat on its surface to impregnate said mat. 2,624,914 11/ 1953 Rhodes 117-111 F 2. The process of claim 1, wherein said succession of 5 2,700,620 11/1955 Somers 118-227 gaps comprises at least four pairs of rollers. 3,029,780 4/1962 Justus et a1 118-249 3,257,226 6/1966 Thwaites 117-111 F References Cited 1,517,606 12/1924 Wiese 117 111 F 1,928,568 9/1933 Loomis 117-111R 2,013,312 9/1935 Supligeau e161.-- 117-111F 1174111911MORA118227'249*451424

Claims (1)

1. A PROCESS FOR THE UNIFORM IMPREGNATION OF A FIBROUS MAT WITH A POLYMER SOLUTION COMPRISING THE STEPS OF PASSING A FIBROUS MAT HAVING A SURFACE THROUGH A SUCCESSION OF SUBSTANTIALLY IDENTICAL GAPS EACH DEFINED BETWEEN PAIRS OF ROLLERS, COATING SAID ROLLERS UNIFORMLY AND CONSTANTLY WITH SAID POLYMER SOLUTION, THE GAPS BETWEEN SAID ROLLERS BEING SUCH THAT SAID FIBROUS MAT IS NOT SUBJECTED TO COMPRESSION THEREBETWEEN BY THE ROLLERS PER SE, MAINTAINING THE CLEARANCE OF SAID GAPS EQUAL TO OR GREATER THAN THE THICKNESS OF SAID MAT, DRIVING EACH OF SAID COATED ROLLERS IN THE SAME DIRECTION AS THE ADVANCING DIRECTION OF THE FIBROUS MAT AT A SPEED AT LEAST TWO TIMES FASTER THAN THE SPEED AT WHICH SAID FIBROUS MAT ADVANCES, AND TRANSPORTING A UNIFORM STREAM OF SAID POLYMER SOLUTION TO SAID MAT ON ITS SURFACE TO IMPREGNATE SAID MAT.

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