CS210569B1 - A method for producing highly fibrillated particles from synthetic polymeric materials - Google Patents

Abstract

The invention relates to a material for the production of fibrous structures such as paper, cardboard or paperboard by wet felting from synthetic materials. In the production of highly fibrillated particles, a solution of synthetic polymer or copolymers is fed into its precipitator in the area of an intense field of mechanical oscillation. This field, which arises at the shaping nozzle of the hydrogenerator, is caused by the kinetic energy of the flowing liquid

Description

The invention relates to a material for the production of fibrous structures such as paper or paperboard by wet felting.

It is known to produce these fibrous formations from synthetic fibers. However, most types of synthetic fibers are difficult to spist and the fibrous formations made from them have low wet strength. The cause of poor felting is poor fibrilability of the synthetic fibers. Somewhat better results are obtained by using fibers with a gel-like porous structure (i.e., non-collapsed fibers).

To improve fiber fibrillation, synthetic fibers are crushed prior to refining (see US Pat. No. 3,364,102). It is also known from US Pat. No. 3,402,231 to increase fibrillation of synthetic fibers by extruding a polymer-water-sodium carboxymethylcellulose mixture into a steam stream. More recently, it is used to manufacture fibrous structures of synthetic fibers, i.e. Fibers, which are tufts capable of felting into a fibrous structure, which are prepared by precipitating synthetic material while crushing and blending (see US Pat. No. 2,999,788) Despite all these processes, the degree of fibrillation and the ability to filament synthetic fibers remain relatively low. The fibrous formations made of these fibers have low wet strength and are difficult to remove from the screen of a paper machine.

These drawbacks are overcome by the present invention. SUMMARY OF THE INVENTION The present invention provides a method for producing highly fibrillated particles from synthetic polymeric materials, wherein a synthetic polymer or copolymer solution is fed to its precipitant in an intense 5-25 kHz field of meohiotic oscillation induced by the moving energy of the flowing fluid.

As synthetic polymeric material for the production of highly fibrillated particles, only synthetic polymeric materials capable of forming solutions that can be coagulated in a suitable precipitant can be used in the process of the invention. These polymeric materials consist essentially of texmethethio resins, condensation polymers containing amide chains (for example polyhexamethylene adipamide, polymetaphenylenylene isealamide copolyamides of about 20% polyhexamethylene adipamide and about 80% polycaproamide amide chains of about 15% polyhexamethylene adipamide); it contains methoxymethylene substituents, condensation products containing ester chains (eg 80:20 ethylene terephthalate / ethylene isophthalate copolyester), condensation polymers containing urethane chains or urea chains, and also addition polymers (eg acrylononitrile, wherein the polymer is a copolymer containing ca. 94% acrylonitrile and 6% methacrylate) as well as plasticized addition polymers (e.g. polyvinyl chloride) and condensation elastomers and copolyamides).

Suitable coagulants are liquids (precipitants) which do not dissolve more than 3 wt. % polymer. The precipitant must not be miscible with the polymer solution in the cases used. Suitable precipitants are, for example, water, glycerin, ethylene glycol, ethyl ether, carbon tetrachloride, triethanolamine, acetone / hexane, dioxane / hexane, aqueous sugar solutions and lower alcohols. A suitable temperature / shrinkage range according to the type of precipitant used is ⁰ - 80 ° C.

210 S6S

The process is performed in a mechanical oscillator generator operating on a hydrodynamic basis using the effect of mechanical oscillation and associated cavitation phenomena. Primary eddy rings are formed at the edge of the forming nozzle. A secondary periodic vortex formation with the opposite sense of coiling to the primary vortex formation occurs on the vibrator located opposite the forming nozzle. Periodic pressure changes are accompanied by cavitation. When cavities arise during cavitation, there are hydraulic impacts with pressure of many tens of MPa. Under these conditions, coagulum, eg, leads to the formation of hydrophiles - which are highly fibrillated (fibrous) particles.

An advantage of the process according to the invention is that the fibrillated particles produced according to the invention have a high degree of fibrillation and a high water absorption capacity. These particles, which are referred to as hydrophiles, are excellent felts, either alone or in combination with other types of fibers, and the fibrous structures formed therefrom on a paper machine screen are readily removed from the screen and processed well.

The invention is described in more detail in the examples below.

Example 1

A solution of copolymers containing 94% acrylonitrile and 6% methyl acrylate in N, N-dimethylformamide is extruded through a nozzle into an aqueous dextrose solution in an intense field of mechanical vibration generated at the edge of the exit cross section of the forming nozzle and on a vibrator. The pressure drop at the forming nozzle is 1.3 MPa. The polymer solution was fed under a pressure of 2.81 MPa.

The solution-precipitant mixture contains about 1.8 wt. % hydrophiles. Upon felting, the hydrophiles then form a bonding system that is comparable in strength to that of pulp fibers.

Example 2

A solution of nylon 66 in 10% formic acid is fed to the precipitation solution, which is a 0.3% sodium carboxymethylcellulose solution, in the region of the primary vortex fingers formed at the edge of the inlet cross section of the shaping nozzle. Precipitation takes place in a mechanical oscillator generator tuned to a frequency of 13 kHz at the tip of the vibrator.

Example 3

A polyurethane solution containing 6% polymer, 4% trichloroacetic acid, 40% formic acid and 50% methylene chloride is extruded into the primary vortex field at the forming pump nozzle. The precipitant is water. The pressure drop across the die is 0.8 MPa.

Example 4

A solution of polyvinyl chloride plasticized with dioctyl phthalate (75% polymer and 25% plasticizer) in N, N-dimethylformamide (10% solution) is fed to the precipitation solution in the field of mechanical oscillations at the exit orifice of the forming nozzle. The precipitating agent is a 20% aqueous glycerin solution with an alkylphenylpolyethylene oxide (wetting agent). The process is carried out at a temperature of ° C. The pressure drop across the die is 1.5 MPa.

Claims (1)

OBJECT OF THE INVENTION Process for producing highly fibrillated particles from synthetic polymeric materials, characterized in that a solution of the synthetic polymer or copolymers is fed to its precipitant in the region of the intensive 5-25 kHz field of meohiotic oscillation caused by the moving energy of the flowing liquid.