FR2561989A1 - LAMINATE MULTILAYER LAMINATE - Google Patents

Abstract

THE INVENTION RELATES TO A LAMINATED AND ARMED SHEET. IT RELATES TO A LAMINATED SHEET INCLUDING A TULLE OF REINFORCEMENT 64 PLACED BETWEEN TWO EXTERNAL TABLECLOTHS 60, 62. ACCORDING TO THE INVENTION, THE TULLE OF REINFORCEMENT 64 IS FORMED BY TRIPLE EXTRUSION OF TWO ADHESIVE AND THERMOS-WELDABLE POLYMERS AROUND A WELD OF A RESISTANT POLYMER, FOR EXAMPLE OF POLYPROPYLENE. APPLICATION TO THE MANUFACTURE OF TOWEL CLOTH.

Description

The present invention relates to a structural product

  in the form of a sheet, reinforced with plastic composite strands, having a layer or a coating (complete, partial or segmented) of a heat-sealable adhesive material, preferably a thermoplastic polymer, as well as its manufacturing process. The strands

  are arranged between layers of a coating material

  external material which may be a plastic film, a sheet, for example of aluminum, a paper, for example coated or filled, a kraft paper, a tissue paper (various thicknesses) or various similar materials

  to leaves and that absorb. In one embodiment

  preferred embodiment, the invention relates to

for absorbent towel.

  The plastic strands used for the reinforcement of the product are formed of a core polymer having a relatively high mechanical strength, for example polypropylene or polyester. The strands have a layer or coating of a heat-sealable adhesive material, for example a polymer which covers

at least partially the strands.

  The strands are preferably prepared by simultaneous extrusion of two or three materials forming

  a composite material, in a special extrusion die

  if we. The strands may be arranged in any form of reinforcing ply, as hitherto used in the art. However, it is very advantageous that they

  are extruded in the form of a plastic mesh.

  The invention is described in more detail hereinafter with reference to an advantageous embodiment constituting a continuous absorbent towel fabric comprising a multi-layer fabric reinforced with a continuous plastic mesh obtained by triple extrusion. The tulle is placed between two layers of paper and, by thermosetting and gluing under pressure, the fabric is

  -prepared in the form of a laminated sheet.

  The continuous extrusion of the tulle of plastic material

  This process began in about 1956 with the method described in Mercer US Patent No. 2,919,467. Since that time, many patents have been issued in the United States of America and in other countries, on improvements and additions made

the continuous extrusion process.

  The initial extrusion process has been developed along two main axes, the first one in which the plastic sheet is extruded and holes are formed therein to obtain a tulle-like structure, and the second in which individual strands of plastic material are extruded and oriented as a connected network forming a structure

  similar to a tulle. The invention relates more specifically

  a variant of this second embodiment.

  Methods for carrying out this technique are already known and, for example, US Pat. Nos. 3,700,521, 3,767,353, 3,723,218, US Pat.

  4,123,491, 4,152,479 and 4,190,692 represent

  and methods of making a tulle

continuous extrusion of strands.

  According to all these patents, a game at least

  strands is extruded through several individual orifices

  tives. a second set of strands of the tulle structure may be extruded by a second set of spaced individual orifices, or a second set of strands may be extruded preferably periodically by a continuous annular slot. In any case, the two sets of strands are extruded so that the individual strands intersect at an angle and form integral connections in the extruded plastics mesh. The resultant extruded flat web obtained

  in an operation, or a tube of tulle of plastic material

  in another operation, is cooled so that the plastics material of the strands hardens, for example in a water bath, and the tulle is removed from the extrusion orifices by right-handed rollers or by another suitable device. traction. It is obvious that the spacing of the strands and their diameter may vary

at will.

  When extruding a tube of tulle, it is usually pulled on a cylindrical mandrel which allows a stretching of the strands and an enlargement of the openings formed in the structure of the tulle. This stretching

  strands on the mandrel provides a preferential orientation

  of plastic, but in practice the

  tulle is characterized in that it is of the non-oriented type.

  In many applications, it is desirable for the tulle strands to be further stretched and for the plastic to be oriented more significantly, and the operation can be performed, for example in the case of a tube of tulle. extruded, by heating and longitudinally stretching the tube so that the strands are elongated and oriented more significantly. The stretching of the tube causes it to sag when stretched longitudinally. When the tube has been split and formed into a flat sheet of extruded tulle, the sheet or flat sheet may be heated and a first set of strands may be stretched and oriented in a first direction and, in a separate second stage, the second set of strands can be stretched so that it is oriented in a second direction. Some tulles of plastic material can be oriented at room temperature but, in practice, the tulle is heated

  so that the orientation is accelerated and facilitated.

  It has been unexpectedly found that individual strands connected, extruded to form tulle-like structures, can be extruded simultaneously even under conditions having

  a high speed gradient, in the form of strands lami-

  composites. The laminar flow of several polymers, using a simultaneous extrusion die which forms individual strands, gives, contrary to expectations, an extruded composite strand which has a laminar structure. It had been assumed that the extrusion of a laminar flow through the relatively small holes of a die, coupled with the mechanical shearing action to which the current is subjected during the formation of the connected strands, would cause a disturbance of the laminar flow and a mixture of polymers with formation of a mixed polymer strand, without the structure

distinctive laminar.

  In a preferred embodiment, the invention relates to a product in the form of a laminated web, having a tulle-like structure and composed of individually stranded strands, each strand being formed of a high strength polymer, coated or coated between outer layers of relatively low temperature softening and heat sealable polymeric material as each strand leaves the three layer type die. Strands and tulle with three layers are called "triple extrusion" in

following this memoir.

  Examples of resins having resistance

  high mechanics, and destined to form the soul, are the poly-

  propylene, high density polyethylene, low density polyethylene, linear low density polyethylene

  and polyester as well as copolymers. The polypro-

  Lene is an advantageous resin at high temperature because it has a low cost and a low orientation temperature. Coating polypropylene or the like with heat-sealable resins such as a copolymer

  of ethylene and methyl acrylate, a copolymer of

  and vinyl acetate or ionomer resins such as "Surlyn", a modified polyethylene marketed by EI DuPont of Nemours Co., and the like form a reinforcing composite material that can be used, between layers of a material external coating, for heat sealing and pressure bonding of the material

  composite, with formation of a sheet laminate.

  Simultaneous extrusion and more precisely triple extrusion of a tulle-like product

256 1989

  in the form of a film is already known as described in US Patent 4,410,587. However, this patent does not suggest that the laminar flow of polymers, by a die having an extrusion slot simultaneous or triple extrusion, can be realized

  for the formation of laminar extrusion composite strands.

  Other features and advantages of the invention will be better understood when reading the

  following description of examples of realization

  and with reference to the accompanying drawings in which: Figure 1 is a section through the vertical axis of a portion of an extrusion die; Figure 2 is an enlarged detail of a portion of the die of Figure 1, in the circled region 2 of Figure 1; FIG. 3 is a perspective of an advantageous product in the form of an extruded tubular tulle, a small part of the tulle being cut along the longitudinal axis so that the process of cutting the tubular tulle and opening for the formation of a flat tablecloth of tulle is represented; Figure 4 is a partial perspective of the flattened tulle shown in Figure 3, on a larger scale; Figure 5 is a section of a strand of the tulle, along the line 5-5 of Figure 4, in greatly enlarged form; Figure 6 is a partial plan view of the plate forming the extrusion die head; Figure 7 is an enlarged partial section of the region marked 7 in Figure 1, the striker being shown in the lower position; Figure 8 is a partial section similar to Figure 7 but in which the striker is in the high position; and Figure 9 is a perspective showing

  the sheet product according to the invention.

  In an advantageous embodiment of the invention, plastic strands are continuously extruded, in the direction of the machine, by a plurality of spaced apertures forming orifices arranged annularly around a die head.

  extrusion. An adjacent continuous orifice placed

  The stretching around the die head is alternately covered and uncovered so that, whenever it is discovered, it forms a connecting strand in the transverse direction. The mechanism that is moved so that it alternately covers and discovers the continuous annular orifice is called "striker" in the remainder of this specification. The extrusion obtained with the aid of the preceding structure is in the form of a tube of plastic tulle which generally has openings of

  rectangular shape, placed along the length of the tube.

  In known manner, the cutting of the tube at the end

  The web is remote from the extruder die and allows a product web to be formed, the web being then subject to orientation or other processing as is well known in the art. We now consider more precisely

  drawings for the description of the manufacturing process,

  in a preferred embodiment using a triple extrusion of an array of composite strands each formed of a laminated extruded structure having a distinct inner layer placed between two outer layers of a polymeric material, placed on either side .

  Referring to Figure 1; a year-round

  The die 10 is of the type known in the art and includes conventional features such as support bolts and adjustment structures (not shown). in a known and common manner. However, the industry presents a difference on an important plane. In the die 10, three reservoirs 18, 20 and 22 of polymeric materials 18a, 20a, 22a (shown in FIG. 2) respectively are held under pressure, the materials being transmitted to the die by an extrusion system (not shown). ), the individual streams of polymeric materials being transmitted to the die 10 as indicated

  to the tanks placed annularly 18, 20 and 22.

  All of these reservoirs communicate and direct a current to a common annular reservoir 24. The reservoir 24 receives the three separate streams of polymeric materials 18a, 20a, and 22a, respectively, which collect in the annular reservoir 24 as a three-layer laminar flow. which leaves the reservoir 24 in a common annular supply channel 26. This

  is shown more clearly in FIG.

  three laminar layers of polymers 18a, 20a and 22a which flow. The three layers flow along the lips of the die with the general reference 28, and form three-layer composite strands constituting a connected network which forms a tulle-like tubular structure 50, as shown on FIG.

Figures 1 and 3.

  The lips 28 of the die are preferably made as shown and have on the upper surface 14 of the die head plate a series of spaced apart spaced bearing surfaces 34 which are better represented in FIG. bearing surfaces forming between them a series of lower nozzle orifices 36 arranged annularly and by which the strands 30 in the direction of the machine are extruded

continuously by the sector.

  We now consider, with reference to Figure 1, the extrusion of the transverse strands 32; the spans 34 of the spinneret plate 14 are separated from a portion 38 of the spinneret 10 so that they form an upper passage 40 above the spans, in the form of a continuous annular orifice placed all around of the sector. An alternative striker 42 is associated with the upper passage 40 of the spinneret and can be lowered and lifted alternately by a suitable device designated by the reference 44 so that the upper passage 40 is covered and uncovered (it is shown in FIG. 1). The striker 42 comes into contact with the upper surface of the staves

34 during his run down.

  When the striker 42 is in its lower position (better represented in FIG. 7), the passage is closed and only the continuous extrusion of the strands in the direction of the machine is effected by the lower orifices 36. which remain always open so that the machine direction spaced apart strands are continuously extruded in an annularly distributed pattern as shown in FIGS. 1 and 3. When striker 42 is raised to its upright position (best shown in FIG. 8), the passage 40 is discovered and allows the extrusion of a

  annular strand 32 in transverse direction.

  The reciprocating movement of the striker 42, which is relatively fast, provides distance extrusion of strands 32 in the transverse direction, connecting the continuous strands 30 which are in the machine direction, so that a tubular structure 50 similar to a

  tulle is formed as shown in Figures 1 and 3.

  The resulting tube formed by the tulle and generally identified by the reference 50, is pulled down, away from the die head 12, preferably on a cylindrical mandrel (not shown) and in a water bath ( not shown), advantageously using rollers (not shown), as known in the art. When the plastics strands have hardened, the tube formed by the tulle is preferably split longitudinally so retort

Z56 1989

  as generally indicated by reference numeral 52 in Fig. 3 and is opened as a flat sheet

  54 a portion of which is shown in Figure 4.

  The sheet may be collected on a roll in a known manner (not shown). According to the invention, the strands extruded with the die of FIG. 1 are composite and have a laminated multilayer structure as shown in FIG. 5, when the polymer 20a is different from the polymers 18a and 22a. The multilayer structure shown is the preferred triple-extrusion triple-layer structure comprising a core polymer 20a disposed between a first outer layer 18a and a second outer layer 22a, both formed of a

  material and which are arranged on both sides.

  The unexpected advantage obtained is due to the fact that the laminar composite structure formed by the three-layer flow in the die body is retained

  and presented by the extruded strands even when the extrusion

  of relatively small strands, in the head 12, despite the action

  shearing provided by the firing pin 12.

  In an advantageous embodiment of the invention, the outer polymer layers 18a and 22a

  may be formed of adhesive polymers of the thermo-

  relatively stable weldable and other heat-sealable adhesive materials that can be selected from the group

  adhesive resins and the like. These materials, when

  that they are in polymeric form, are of a type whose softening temperature is lower than that of the core polymer, and they comprise for example an ethylene-methyl acrylate copolymer, an ethylene-vinyl acetate copolymer and the Thermoplastic polyvinyl chlorides as well as polyamides. In other embodiments, they may include hot melt adhesives, ionomeric resins such as "Surlyn" sold by E.I. DuPont de Nemours Co.,

  thermoplastic rubbers such as "Kraton", commercially

  by Shell Chemical Co., Houston, Texas, and the like.

  The term "polymer" is used herein in its general sense which embraces copolymers. A very advantageous polymer is a copolymer of ethylene

and methyl acrylate.

  The polymeric core material 20a may be selected from the polymers generally described herein as high strength polymers, and may be selected from the group consisting of, for example, polypropylene, polyethylene,

  polybutylene, polyesters, "Nylons" and the like.

  It should be noted that the invention is not limited to the use of the above-mentioned groups of materials and that there is a considerable number of copolymer polymers and the like which fall into the category of core polymers and the category of adhesives

heat-sealable, respectively.

  In the form made by triple extrusion, a very advantageous combination comprises a core layer 20a of polypropylene, and the two outer layers 18a and 22a consist of a copolymer of ethylene and methyl acrylate or a copolymer ethylene

  and vinyl acetate, the former being preferable.

  This particular combination of materials, after

  biaxial structure, is an excellent armouring

  triple extrusion die useful for fabric reinforcement and other sheet product, for placing between two layers of outer fabric, such as paper, fabric, sheet or the like as shown in Fig. 9. Outer layers of fabric are indicated by the references and 62. The structure of the reinforcing mesh has the reference 64. The copolymer of ethylene and methyl acrylate or the other material identified by the references 18 and 22a has the advantage to exhibit an adhesion and thermofusibility function providing a connection of the reinforcing structure by heating to the layers

256-1989

  1 1 external 60 and 62 when the composite assembly is heated and compressed. Materials do not need to be

18a and 22a are identical.

  As previously indicated, any flexible outer coating material such as aluminum foil, polyester film, "nylon" film, "Cellophane" film, paper, oriented polypropylene, foil acetate or the like may be used as the outer coating of the laminate. An absorbent paper is preferable for toilet paper. An advantageous material for this purpose is available from Scott Paper Company, and has a basis weight of 15 to 31 g / m 2 in two, three and four layers. Another absorbent material that can be used according to the invention is described in the US patent

of America No. 4,296,161.

  The most advantageous heat-sealable material is the copolymer of ethylene and acrylate. methyl, of which several types are available from Gulf Oil

  Chemicals for example types 2205, 2255 and 2207T. Enjoyed-

  several types of copolymers of ethylene and vinyl acetate are available from E.I. DuPont de Nemours

  & Co., including types 3180, 3175 and 3190.

  The pressure welding and the connection by heating as indicated above are satisfactory

  for the preparation of the laminates according to the invention.

  The operation can be carried out generally by various devices, for example by contacting opposite faces of the assembly or the composite material.

  with cylinders or heating trays.

EXAMPLE 1

  This example relates to a tulle formed by polypropylene triple extrusion with DuPont copolymer of ethylene and vinyl acetate # 3180 and a paper

  "Scott" as previously described in two layers.

  A heating roll temperature of 93 to 121 ° C is used for thermal bonding and pressure bonding.

EXAMPLE 2

  This is a polypropylene triple extrusion tulle with DuPont # 3175 ethylene vinyl acetate copolymer and "Scott" material as previously described in two plies. The temperature

  heating cylinders was 93 to 121 C.

EXAMPLE 3

  A triple extrusion tulle is prepared from Dupont polypropylene and copolymer of ethylene and vinyl acetate # 3190 and the material

  "Scott" as previously described, in two thicknesses.

  The temperature of the heating rolls was 93 to 121 ° C

EXAMPLE 4

  Triple extrusion tulle was formed with polypropylene and copolymer of ethylene and methyl acrylate No. 2205 from Gulf Oil Chemicals. The temperature of the heating rolls was between 105 and

1210C.

TESTING

  The results of the following peel tests were obtained by separating the layers of the laminate

  and by measuring the force required for separation.

  The force is expressed in Newtons and is indicated in standardized form according to the number of strands

  and the adhesive coating mass, for comparison.

  Example 1 Example 2 Example 3 Example 4

0.344 * 0.162 *. 0.196 * 0.278 *

  * N / brin.g / m2 These peel tests give very good results

  favorable to those of a pre-absorbent

  adorned conventionally using the same paper,

  of a latex-based adhesive and a single layer of

  ture of reinforcing plastic tulle which, during the peel test, give a strength of

0.02 N only.

  Of course, various modifications can be made by those skilled in the art to the devices and methods which have just been described solely as examples.

  non-limiting without departing from the scope of the invention.

Claims (10)

  A reinforced multilayer laminate, characterized in that it is prepared by heat sealing and press-bonding a composite assembly comprising a reinforcing network layer (64) consisting of connected thermoplastic strands, placed between layers (60, 62) of an outer material, the strands (30, 32) consisting of an inner core of a first polymer carrying an outer adhesive layer heat-sealable type.   2. Laminate according to claim 1, characterized   rised in that the network formed by the strands is a tulle extruded and oriented.   3. Laminate according to claim 1, characterized   in that the strand structure is of a lami-   formed by triple extrusion, from at least two different polymers, the inner core polymer (20a) having a softening temperature higher than that of the outer polymer, the outer polymer (18a, 22a) comprising layer   arranged in opposite directions on the soul.   4. Laminate according to claim 3, characterized   in that the core polymer (20a) is polypropylene.   lene, and the outer polymer is a copolymer of ethylene and methyl acrylate.   5. Laminate according to claim 3, characterized   in that the outer material (60, 62) is of absorbent type.   6. Laminate according to claim 3, characterized   in that the outer covering material (60, 62) is a paper cloth.   Laminate according to claim 4, characterized   in that the core polymer (20a) is formed of polypropylene and the outer polymer is formed of a   copolymer of ethylene and methyl acrylate.   8. Laminate according to claim 1, characterized   in that the core polymer (20a) is the polypro- pylene.   9. Laminate according to claim 1, characterized   in that the outer adhesive layer is formed   a copolymer of ethylene and methyl acrylate.   10. Laminate according to claim 1, characterized   in that the core polymer is formed of polypropylene and the outer adhesive layer is formed of a copolymer   ethylene and methyl acrylate.