NO131089B - - Google Patents

Description

Flame-resistant cellulose products and

method for the production thereof.

The present invention relates to flame-resistant cellulose products, such as paper and paper products, with excellent tensile

firmness, improved tear strength, improved elongation, especially in the transverse direction, as well as a fabric-like draping ability and softness.

These products can be produced according to the invention by a simple

and economic procedure.

There has been and is an ever-increasing need for disposable

products of fabric. This is particularly the case in various medical areas, as more particularly in modern hospitals where disposable sheets, masks, duvet covers, pillow covers etc. have been widely used.

Furthermore, there is an ever-increasing need for disposable aprons, towels, coats, etc., in companies or facilities where food is processed, etc. Even within the clothing industry, there is an increasing need for cheap disposable fabrics for the production of work clothes, shirts, underwear, etc. Also within the grocery industry there is a growing need for disposable materials, such as for the production of curtains, tablecloths, handkerchiefs etc. There are a number of such products either in the form of a simple paper structure or as a multi-layered paper structure or as laminated products where several papers are glued together into plate-like or fabric-like materials, and these can in turn be strengthened with the help of films, threads, nets or other reinforcing materials.

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that cheap materials must be used so that disposable use can be defended. The first step in this direction was to replace woven fabrics with non-woven fabrics, but even these fabrics are relatively expensive and in a number of cases have not been very widely used for disposable products due to the costs.

A somewhat ideal solution would be achieved if paper or paper-like products could be used instead of woven or non-stretch woven fabrics. However, with regard to physical properties, paper has a number of serious disadvantages. Paper and paper products thus represent a very serious flammability problem. Furthermore, they normally lack the tensile strength and tear resistance found in more common woven fabrics and do not normally have the softness and flexibility found in such fabrics either.

In the past, a number of efforts have been made to

to improve paper and paper products so that one can reduce their flammability characteristics while at the same time trying to improve their tensile strength, elongation characteristics and tear strength in addition to improving their softening and flexibility. Up until now, it has been possible to improve paper and paper products with regard to one of these properties, but such an improvement has usually occurred at the expense of one or more other properties.

There. is thus a main purpose of the present invention to provide paper and paper products with reduced flammability, improved tensile strength, elongation characteristics and improved tear strength, in addition to increasing their draping ability and softness.

According to the present invention, a flame-resistant cellulose product with improved tensile strength and tear strength has thus been provided. improved drag ability and flexibility. oe this product is characterized by the fact that it comprises 35-75 weight-? cellulose material, 2-25 wt-? of a cross-linked polymeric acrylic resin, 7-15 wt. ammonium bromide and 1-25 wt-? of a weakly basic, water-soluble, aliphatic, nitrogenous compound containing at least one amino group, in particular urea or dicyandiamide, and, if desired, up to 20 wt. of other additives of a known nature.

According to the invention, a method for the production of this cellulose product is also provided, and this method is characterized by the fact that a cellulose material is applied to an aqueous treatment agent comprising 3~30 wt. of a cross-linking polymeric acrylic resin, 4-20 wt. ammonium bromide and 1-20 wt. of a weakly basic, water-soluble, aliphatic, nitrogenous compound containing at least one amino group, in particular urea or dicyandiamide, and,

if desired, up to 20 weight-? of other additives of a known nature, after which the product is dried and cured.

As mentioned, the amine-containing compound includes urea,

and further derivatives of urea such as methylurea, ethylurea, 1,1-dimethylurea, 1,3_diethylurea, thiourea, derivatives of thiourea such as 1-methylthiourea, 1,3-diethylthiourea, 1,3-dimethylthiourea, aminourea (semicarbazide), diaminourea (cabazid ), and iminourea (guanidine) and dicyandiamide (1-cyanb-guanidine).

It is obvious that these components should preferably be used in a one-bath impregnation process as this is easier, more appropriate and more efficient. If, however, it is desirable under certain circumstances, then the components can be applied separately in a row to the following impregnation bath. As this is less economical, less appropriate and less effective, this method should only be used in very special cases.

The aforementioned cross-linking polymeric acrylic resin saturates and impregnates the paper and paper products and improves their tensile strength, improves tear strength and elongation and gives the products better draping ability and softness. Especially well suited for this purpose are e.g. ethyl acrylate polymers, methyl acrylate polymers, ethyl hexyl acrylate polymers, butyl acrylate polymers, ethyl acrylate-methyl methacrylate copolymers, ethyl hexyl acrylate methyl methacrylate copolymers, butyl acrylic-methyl methacrylate copolymers, ethyl acrylate-polyvinyl acetate copolymers

and ethylhexyl acrylate-polyvinyl acetate copolymers.

The polymeric acrylic resin is normally applied to the paper or paper products in the form of an aqueous emulsion or latex and may be added to the impregnation bath in such quantities that a concentration of the polymeric acrylic resin with respect to solids from 3 wt. and up to 30 weight-? of the total impregnation bath. In the preferred method, however, from 7 to 13 wt. of the polymeric acrylic resin (calculated on a solids basis).

Flame retardancy comprising a reduction in the rate of combustion or a prevention of complete flame combustion or a reduction in the afterglow is imparted to the paper or paper products by a selective combination in which there is a specific proportion of (1) the water-soluble inorganic salt, namely, ammonium bromide and (2) the weakly basic water-soluble organic nitrogen-containing amino compound such as urea, derivatives of urea such as methylurea, ethylurea, 1,1-dimethylurea, 1,3-diethylurea, thiourea, derivatives of thiourea such as 1-methylthiourea, 1,3-diethylthiourea, 1 ,3" dimethylthiourea, aminourea (semicarbazide), diaminourea (carbazide), immunourea (guanidine), and dicyandiamide (1-cyanoguanidine). It has been found that such a combination does not in any way affect the flexibility or softness of the paper or paper products or produce other undesirable properties or characteristics, or affect the stability of the acrylic resin emulsion.On the contrary, it has been found that ammonium bromide-amino-containing combination provides the desired flame-resistant properties and characteristics while at the same time obtaining an unexpected improvement with regard to the softness and flexibility of the paper or paper products. Ean has also been able to observe that, in addition to the properties that each of the compounds ammonium bromide and the amine-containing material individually gives the product, a certain synergistic effect is also achieved in the combination of said compounds, which contributes to giving the product an improved textile-like quality.

The ammonium bromide is preferably added to the impregnation bath in such quantities that a concentration of from 5 to 9 wt. ammonium bromide in the impregnation bath.

The amino-containing compound is added to the impregnation bath preferably in such quantities that a concentration of

3 to 6 weight-? in relation to the total weight of the impregnation bath.

The polymeric acrylic resin emulsion containing the added ammonium bromide and the amino-containing compound can be applied to the paper or paper products by a known impregnation or coating technique. If desired, e.g. the paper or paper product is fed from a roll or similar and then into the impregnation bath, completely immersed in it so that the necessary absorption of material is obtained. If, however, it is desirable for other reasons, the paper or paper products can be fed between an upper rotatable pressure roller and a lower rotatable immersion roller which is placed partly in the impregnation bath from which it carries material and transfers this to the paper or paper products at the confluence between the upper pressure roller.

The amount of aqueous treatment agent that the paper products or the paper can absorb varies within very wide limits, i.e. normally from 75 wt. to 250 weight-? based on the weight of the paper or paper product. In the preferred embodiments, however, the absorption of the aqueous treatment agent will normally vary from 17 5 weight-? to 225 weight-? based on the weight of the paper or paper product.

However, there are heavier paper or paper products where it is desirable not to have such a large absorption as mentioned above of the mentioned aqueous treatment agents, as this requires great problems when removing water during drying. In such cases, it is more desirable to use impregnation baths containing higher concentrations of said components and then have a lower absorption, i.e. only from 75 to 150 wt. in relation to the weight of the paper or paper products.

It is obvious that other materials can be added to the impregnation bath in order to produce certain properties or characteristics in the paper or paper products. Such materials can include substances for producing opacity, absorption-regulating agents such as water-repellent agents, in addition to fillers, wetting agents, dyes or pigments, softening agents, perfumes, flavorings etc.

The treated paper or paper product can be dried at the desired temperature, e.g. using an aqueous air top-heated oven or dryer capable of being heated to a sufficiently high temperature to dry the paper or paper product;

normally, temperatures varying from 115° to 165°C will be used

all depending on the speed of the paper or paper product through the drying zone or over the dryer.

After drying, the finished paper or paper product will contain from 35 Ml 75 weight-? of the cellulose material itself, from 2 to 25 wt. of the polymeric acrylic resin, from 7 to 15 wt. ammonium bromide and from 1 to 25 wt. of the amine.

If desired, the paper or paper products may also comprise up to 20 wt. of other additives as mentioned above.

Paper or paper products that can be processed in accordance with the present invention may include paper or paper JuKierso:r. is intended to be used for packaging, writing or printing, building or construction purposes or for applications in various medical areas, for food processing or processing, in the clothing industry or for the manufacture of household products or any other application where a manufacture, processing, treatment, storage or application of such products include a flammability problem. Such products exist as simple paper structures or as multi-layered paper structures or as laminated products where several of such structures are attached to each other so that plate-like or fabric-like materials are formed and where these can be strengthened with the help of films, threads, nets of different types or other reinforcing materials.

Although the present invention is essentially described with regard to disposable paper or disposable paper products,

then, of course, the invention is not only limited to such products. It should be pointed out that in the manufacture of the present products water-soluble, flame-resistant treatment agents are used,

so that an external exposure to moisture, be it in the form of pure rainwater or in the form of wet washing, will lower their flame resistance to a fairly significant extent. However, it will be possible to find many applications where exposure to moisture or water is not particularly important. For such specific applications, the products will be flame resistant throughout their lifetime. This property is further improved by the fact that ammonium bromide is non-hygroscopic and largely unaffected by varying humidity, says Iser.

The invention will be described in the following examples

in more detail with reference to creped paper, either in a single layer or in the form of several layers, and where the basis weight of the paper will thus vary from 12.5 to 125 g/m <2> oe with stretch levels varying from 5 to 50%. The invention can also be applied to laminated structures consisting of one or more layers of creped cellulose paper where each individual layer has a basis weight from 12.5 to 62 g/mo and which can be reinforced with the help of films, threads, nets, plastic materials etc., and where said materials can have a basis weight of from 3.6 to 36 g/m 2. The total weight of such laminated structures, after gluing together, will normally vary from 25 to 250 g/m p.

Example 1.

Single creped cellulose paper with a basis weight of approx.

32 g/m<c> was immersed at room temperature in an aqueous impregnation bath containing ammonium bromide, urea, a self-crosslinking vinyl acetate ethyl acrylate polymer latex ("X-Link Resyn 2873")- Sufficient amounts of these materials and sufficient water was added to the bath so that: (1) the polymeric acrylic resin was present in an amount which is approx. 20 wt-E of the impregnation bath, (2) the ammonium bromide was present in an amount which amounted to approx. 12 weight-? of the impregnation bath, and (3) urea was present in an amount amounting to approx. 10 weight-? of the impregnation bath.

The creped paper absorbs approx. 100 weight-? of the wet treatment agent. Drying and curing takes place in a heated oven at temperatures varying from 125° to 160°C.

The dried paper product contains 70.4 wt. of base cellulose material, 14.0 wt-? polymer acrylic resin, 8.6 wt-? ammonium bromide and 7.0 wt-? urea. All materials in this and subsequent examples were dried and then oven-fired at 115°C for 10

my. before testing.

Materials were tested in a flame resistance vertical test (TAPPI T--461 os-68) and the burn length was determined to be only 6.2 cm, which is below the required approval value of 13.t: cm and well below the desired value of 11 cm. You got essentially no after-glow. This test consists of hanging a piece of material measuring 6.7 x 21 cm with the longest dimension vertically. A Bunsen or Tirrill gas burner with a flame width of 3j2 cm and with the air supply closed is placed immediately below the sample with the top of the burner approx. 16 mm from the bottom edge of the sample. The burner is switched on for 12 seconds. and then extinguished. The charred length is then measured. The "afterflame" is the time in seconds required for the flame to stop burning. "The Afterglow"

is the time in seconds required for the sample to stop glowing.

The material also passed the flame resistance test described in ASTM D-777 and AATCC Spee. no. 34-1952 which is essentially of a similar type to that described above. The treated paper has a distinct fabric-like flexibility and softness, as this could be determined with the help of 6 laboratory technicians. The tensile strength of the machine direction increases from 195 to 640 g/cm width. In the transverse direction, it increases from 69 to 145 g/cm width. The wet tensile strength in the machine direction increases from 47 to 445 g/cm width. The wet tensile strength in the transverse direction increases from 15 to 143 g/cm width. The extension in the machine direction increases from 21.8 to 30.3?. The elongation in the transverse direction increases--from 4.3 to 9.8%.

The permeability of the creped cellulose paper is essentially not reduced by the flame resistance treatment, as the openings in the fabrics remain unfilled. The creped cellulose paper can be very easily processed in different types of equipment and can easily be cut, folded, printed on or otherwise processed. It is very well suited for the manufacture of pillowcases and duvet covers as it is flame resistant or retarding, soft and strong and sufficiently tough to withstand a significant load without breaking.

Example 2.

The procedure from Example 1 was followed as indicated there, except that the aqueous impregnation bath contained 20 wt. polymer acrylic resin (solids), 16 wt-? ammonium bromide and 1 wt-? urea. The finished dried product contained 63 wt. of the cellulose substance, 15 weight-? polymer acrylic resin, 11 wt-? ammonium bromide and 1 wt-? urea. The vertical flame resistance was 8.7 cm.

The treated product had an excellent textile-like consistency and softness as subjectively judged by 6 independent persons. The dry tensile strength in the machine direction increased from 105 to 645 g/cm width, in the transverse direction the dry tensile strength increased from 69 to 205 g/cm width. The wet tensile strength in the machine direction increased from 47 to 485 g/cm width. Furthermore, the same property increased in the transverse direction from 15 to 148 g/cm width. The extension in the machine direction increased from 21.8 to 26.5?. The extension in the transverse direction increased from 4.3 to 8.3?. Other properties and characteristics were also improved, especially those indicated in example 1.

Example 3-

The procedure from Example 1 was used except

that the aqueous impregnation bath contained 20 wt. solids of the polymeric acrylic resin, 16 wt-? ammonium bromide and 5 wt-? urea. The finished dried product contained 71.0 wt. of the cellulose substance, 14.2 wt-? polymer acrylic resin, 11.3 wt-? ammonium bromide and 3.5 wt. urea. The flame resistance in the vertical direction was 8.6 cm. The treated product had an excellent fabric-like consistency and flexibility as determined subjectively by 6 independent persons. The dry tensile strength in the machine direction increased from 195 to 640 g/cm width. In the transverse direction, the same property increased from 69 to 208 g/cm width. The wet tensile strength in the machine direction increased from 47 to 465 g/cm width. The same property increased from 15 to 137 g/cm width in the transverse direction. The extension in the machine direction increased from 21.8 to 26.2?. The extension in the transverse direction increased from 4.3 to 9.2?. The other properties and characteristics were comparable to those obtained in the product from Example 1.

Example 4.

The procedure from Example 1 was used except

from the fact that the aqueous impregnation bath contained 20 wt. polymeric acrylic resin (calculated on the basis of solids), 16 wt. ammonium bromide and 10 wt # of urea. The finished, dried product contained 68.5 wt. cellulose fiber, 13.7 wt-? polymer acrylic resin, 10.9 wt-? ammonium bromide and 6.9 wt-? urea. The vertical flame resistance was 7.4 cm. The treated and finished product had an excellent textile-like consistency and softness as this could be subjectively judged by 6 independent persons. The dry tensile strength in the machine direction increased from 195 to 710 g/cm width. In the transverse direction, the same property increased from 69 to 170 g/cm width. The wet tensile strength in the machine direction increased from 47 to 495 g/cm width and it increased from 17 to 117 g/cm width in the transverse direction. The extension in the machine direction increased from 21.8 to 27.5/5. The extension in cross-

the direction increased from ^ , 3 >il 9.7?- Other properties and characteristics were as for the product in ?a. example 1.

Example 5>

Fremeanesmått i from exem Part 1 was essentially dirty, except that the watery impregnation bath from the beginning had the following composition:

Five samples were impregnated with said composition. The

the first two samples had a wet absorption of approx. 250 weight-? in relation to the samples. The content of solids in the bath was then reduced approx. 35% by adding 324 kg of water to a bath that weighed 620 kg.

The subsequent wet absorption was maintained at approx. 250 weight-? in relation to the weight of the sample. After drying, the composition of these samples was examined with the following results:

The five samples were accelerated fired in an oven at 115°C

for 10 min. and then tested for flame resistance, and all the samples passed the said test. There was no ignition. 7<V>°PI T-461 os 68, flame resistance. Others were also examined in the five samples with the following results:

These properties can be compared with the corresponding properties for untreated samples, as stated below

These three untreated samples did not pass the A/TX test

It appears from the above results that the treated samples were superior to the untreated ones with respect to all properties.

Oak sample 6.

The procedure from Example 1 was used except that

■: en seI v t v c- vi- l i ndenne v i ny 1 h cet a:.- ety i a kry lat": .--r-; - -■ 1 r- r -' :: r vi.:p-" X-Link Resyn 2833" which contains a larger amount of the ethyl acrylate component. The composition of the treatment bath was as follows:

The absorption level remained at approx. 255 weight-? in relation to the weight of the sample. After drying, the samples had the following composition:

The sample was oven-fired at 115°C for 10 min. and then tested for flame resistance. There was no ignition. TAPPI T-461 os-68 flame resistance. The treated sample had an excellent textile-like consistency and softness as subjectively judged by 6 independent persons. The dry tensile strength in the machine direction increased from 195 to 545 g/cm width. In the transverse direction, the same property increased from 69 to 122 g/cm width. The wet tensile strength in the machine direction increased from 47 to 320 g/cm width, while the same property in the transverse direction increased from 15 to 77 g/cm width. The elongation in the transverse direction increased from 4.3 to 16.0?, while the internal tear strength in the machine direction increased from 24 to 31 g. Other properties of the finished product were of the same order of magnitude as stated for product example 1.

Example 7-

The procedure from Example 6 was followed as indicated, except that two samples of a 2-layer p::oir were used. Each sample had a total basis weight of 36 g/m .

After drying, each sample had the following compositions:

The samples were oven-baked at 115°C for 10 min. and then tried

for flame resistance. TAPPI T-461 os-68 flame resistance. There was no ignition. The finished product had an excellent textile-like consistency and softness as subjectively judged by 6 independent persons. The dry tensile strength in the machine direction increased from 204 and 234 respectively to 920 and 910 g/cm width. The dry tensile strength in the transverse direction increased from 110 and 105 g/cm width respectively to 292 and 310 g/cm width.

The wet tensile strength in the machine direction increased from 38 g/cm

width to 550 and 460 g/bm width. The wet tensile strength in the transverse direction increased from 14 to 15 g/cm width respectively to 155 and 132 g/cm width respectively. The extension in the transverse direction increased from 3.9 and 4.3? to 16.0 and 15.5? respectively. The internal resistance in the machine direction increased from 24 and 23 g to 54 and 43 g respectively.

Other properties and characteristics were improved in a similar way.

Example 8.

The procedure from example 1 was used except

that the cellulose product consisted of a three-layer reinforced laminated fabric consisting of the following: an outer layer of a creped cellulose paper (each of which had a basis strength of 32 g/m p) and a central layer of 8x8 gauze (with an equivalent basis weight of 12.5 g /m 2) and a fastening agent that bound the three layers together into a laminated structure with a basis weight of 86 g/m 2.

The impregnation bath used had the following composition:

"Rhopex RC-5I0" is a self-crosslinking copolymer of ethyl acrylate and methyl methacrylate.

The wet absorption from the impregnation bath was approx. 140 weight-? based on the weight of the cel '.ul Jse product. Absorption:. nen of solids was approx. 20 weight-? tased on the weight of the cellulose product. This corresponds to a dry absorption of 12.5 weight-? ammonium bromide,

4.2 weight-? urea and 2.5 vekr, -? acrylic resin. The resulting product passed all TAPPI and ASTM flame resistance tests. In the same way, other physical properties and characteristics were improved.

Example 9-

The procedure from Example 1 was used except

that urea was replaced with approx. 5 weight-? dicyandiamide in the impregnation bath.

The resulting product was flame resistant and had a textile-like consistency and softness as subjectively judged by 6 independent persons. The product otherwise had physical properties and characteristics of the type specified for the products from example 1.

Example 10.

The procedure from Example 1 was used except

that urea was replaced with approx. 5% aminourea (semicarbazide) in the impregnation bath.

The resulting product was flame resistant and had a textile-like softness and consistency as subjectively judged by 6 independent persons. The product otherwise had physical properties and characteristics of the same type as stated for the products from example 1.

Example_ 11.

The procedure from example 1 was used except

that urea was replaced with an equivalent amount of thiourea.

The resulting products were flame resist<t>e and had

a textile-like consistency and softness as this could be subjectively judged by 6 independent people. The products otherwise had physical properties and characteristics of the type specified for the products in example 1.

Claims (2)

Example 12. The procedure of Example 1 was used except that the self-crosslinking acrylate resin was replaced with an equivalent amount of a copolymer of ethylhexyl acrylate and methyl methacrylate. The resulting products are flame resistant and have a textile-like softness and consistency as subjectively judged by 6 independent persons. The products otherwise have physical properties and characteristics of the same type as those listed for the products in example 1. Example 13- The method of example 1 was used, except that the self-crosslinking acrylate resin was replaced with a corresponding amount of a copolymer of 2-.y lacacrylate and methy Imatetacrylate. The resulting products are flame resistant and have a textile-like consistency and softness as this could be subjectively judged by 6 independent people. The products otherwise have physical properties and characteristics of the same type as for the products from example 1. Example 14. The method of Example 1 was used, except that the self-crosslinking acrylate resin was replaced with a self-crosslinking vinyl acetate-ethylhexyl acrylate copolymer. The resulting products are flame resistant and have a textile-like softness and consistency as this can be judged subjectively by (S independent persons. Otherwise, the products have physical properties and characteristics of the same type as indicated for the products in example 1. P_a_t_e_n_t_k_r_a_v 1. Flame resistant cellulose product with improved tensile strength, tear strength, improved draping ability and softness, characterized in that it comprises 35-75 wt.-? cellulose material, 2-?5 wt.-? of a cross-linked polymeric acrylic resin, 7-15 wt.-? ammonium bromide and 1-25 wt-? of a weakly basic, water-soluble, aliphatic, nitrogenous compound containing at least one amino group, especially urea or dicyandiamide, and, if desired, up to 20 weight-55 of other additives of a known nature. 2. Procedure: 1 production of a cellulose product as specified in claim 1, 3-characterized by a cellulose material applying: an aqueous treatment agent comprising 3-30 wt. of a cross-linking polymeric acrylic resin, 4-20 wt. ammonium bromide and 1-20 wt. of a weakly basic, water-soluble, aliphatic, nitrogenous compound containing at least one amino group, in particular urea or dicyandiamide, and, if desired, up to 20 wt. of other additives of a known nature, after which the product is dried and cured.