IE83311B1 - Process for producing adhesives, and adhesive compositions - Google Patents

Description

PROCESS FOR PRODUCING ADHESIVES. AND ADHESIVE COMPOSITIONS Technical Field The present invention relates to an improvement in the production of adhesive products to reduce or eliminate dusting of the adhesive. The process is particularly suitable in the production of adhesives based on starch, cellulose and its derivatives such as methyl cellulose, which are of particular use as wallpaper adhesives and poster adhesives. The process is also suitable for use in the manufacture of other adhesives, for example cement- based tile adhesives or grouts. The invention also relates to adhesive compositions useful in these applications.

Background Art It has been known to formulate wallpaper adhesives using starch, cellulose and its derivatives such as methyl cellulose either in their pure forms or in combinations of these materials. Where a combination of materials is used they are usually only mixed together in large drum—mixers. Starch based products are relatively cheap but lack adhesive strength, their workability is poor and their yield generally unsatisfactory. Furthermore, they tend to break down quickly under bacteriological attack. Thus the finished adhesive can no longer be used and wallpaper applied with this adhesive is subject to fungus growth.

Cellulose derivative based adhesives exhibit greater yield and adhesive strength, and the workability is much improved. However, the salt content must be considered as a high salt content does not only result in blotting but also in lumps in the powder adhesive due to water absorption. The salt also corrodes wallpaper adhesive application machines.

Pure saltlree cellulose derivatives tend to be rather expensive.

Wallpaper adhesives based on pure methyl cellulose are considered by far the best with regard to adhesion, workability, but they are very expensive to produce.

All raw materials mentioned are generally supplied as flakes or granules, varying in size from 1 micron to several millimetres producing bulk density of 300kg to 900kg.

When making up such an adhesive prior to its application, the adhesive in powder form is mixed with a specified quantity of water. Some adhesives are rejected by professional wallpaper hangers because of excessive dusting when being poured into the water.

This dusting is due to the physical properties of the raw materials used to formulate the wallpaper adhesive. The excessive dust can also lead to difficulties in production where expensive dust extraction systems must be used in order to safeguard the health of the employees.

Canadian patent application no. 2,114,194 relates to a coating composition comprising a tackifier, an organic oil, and an adhesion agent. The coating composition is applied to granular material to reduce dust generation during subsequent processing steps.

The coating composition is applied to hot granules while the granules are being cooled.

The application does not address the problem of dust generation during the production of an adhesive composition in powdered form. Nor does it disclose an adhesive composition suitable for the applications to which the compositions of the present invention are put.

Object of the Invention It is an object of the invention to overcome the aforesaid disadvantages, and to provide an improved process for the preparation of adhesives in which dusting is reduced or eliminated. It is also an object of the invention to provide substantially dust-free adhesive compositions.

Summarv of the Invention Accordingly, the invention provides a process for the production of a substantially dust—free adhesive powder composition which comprises admixing adhesive components in dry powder form to produce a homogeneous adhesive composition characterised in that a coating agent, in the form of a fine mist, is sprayed onto the adhesive component(s) during the mixing step to bind dust particles present in the dry powder mixture. The invention also relates to adhesive compositions made by the aforesaid process.

The adhesives of the invention are found to have good dusting characteristics, resulting in a cleaner production environment. It has been found that the finished product does not dust when poured into water, in contrast with conventional adhesives.

The coating agent may be selected from one of the following materials: polyglycols, for example polyethyleneglycol or polypropyleneglycol; polyetherpolyols of a molecular mass of between 100 and 6000 atomic mass units particularly those based on the aforementioned polyglycols; carbohydrates based on paraffin oil or aromatic and naphthenic oils and terpenes with a boiling point of greater than 2000C and an evaporation number of larger than 100; esters of saturated and unsaturated fatty-acids with C13 to C30 chains, in particular esters of phthalic acid, adipic acid, sebatic acid, oleic acid and linolenic acid; mixtures of the aforementioned esters with alcohols, such as methanol, ethanol, butanol, glycerine, glycol, ethylhexanols, octyl alcohol and fatty alcohols such as those produced from the aforementioned fatty-acids; esters of phosphoric acid with C4-Cm alcohols; phenolsulphonic acid ester and silicone oils with a molecular mass of between 100 and 10,000 atomic mass units.

Preferably, the coating agent is a polyglycol material as outlined in the previous paragraph.

In the preparation of a wallpaper or poster adhesive, the adhesive comp0nent(s) may be selected from one or more of starch. cellulose, a cellulose derivative. particularly methyl cellulose.

In addition to the one or more adhesive components, an adhesive according to the present invention may additionally comprise a clay component, characterized in that both the adhesive component, or components, and the clay component are coated with a coating agent.

The inclusion of a clay compound in adhesives of the present invention, which would be expected to contribute to dusting in a conventional composition, represents a considerable commercial advantage, allowing for the possibility of replacing a proportion of one or more of the more expensive components.

Preferably, the clay component comprises up to 25% by weight of the adhesive prior to its addition to water or some other suitable carrier.

In the case of a cement—based adhesive, the adhesive components may comprise cement, silica sand, silica flour, methyl cellulose. A pigment may also be included.

The process may be carried out by admixing the adhesive component(s) in a drum mixer. The coating agent is sprayed onto the component(s) during mixing in the form of a fine mist, for example using a spray bar having very small perforations.

It has been found that using the process of the invention enables adhesive formulators to use raw materials of much finer particle size making a wider range of grades suitable for use in formulations. The wallpaper adhesives produced by the preferred process of the invention is also found to be smoother and can be spread easier over the wallpaper than conventional adhesives.

The following non-limiting Examples are illustrative of compositions of the invention. Comparative examples of typical conventional compositions are also given: Example 1 - Wallpaper Adhesive - 100% Starch - 100% CMC - 20% China clay — 10% Coating fluid Example A.

Comparative Example of Conventional Wallpaper Adhesive O - 100% Starch 0 - 100% Carboxy methyl cellulose Utilising the composition of Example 1 instead of the conventional composition of Example A represents a cost saving in the raw materials of the order of l0 - 40%.

Example 2 ~ Tile adhesive/grout % - 70% Cement % — 30% Silica Sand 80% - 30% Silica Flour - 10% Methyl cellulose 0 - 15% Pigment - 10% Coating Fluid Example B Comparative Example of Conventional tile adhesive/grout % — 70% Cement % — 30% Silica Sand 80% — 30% Silica Flour - 10% Methyl cellulose 0 -15% Pigment

Claims (13)

1. A process for the production of a substantially dust-free adhesive powder composition which comprises admixing adhesive components in dry powder form to produce a homogeneous adhesive composition characterised in that a coating agent, in the form of a fine mist, is sprayed onto the adhesive component(s) during the mixing step to bind dust particles present in the dry powder mixture.

2. A process as claimed in Claim 1, characterised in that the coating agent is selected from: polyglycols, for example polyethyleneglycol or polypropyleneglycol; polyetherpolyols of a molecular mass of between 100 and 6000 atomic mass units particularly those based on the aforementioned polyglycols: carbohydrates based on paraffin oil or aromatic and naphthenic oils and terpenes with a boiling point of greater than 200°C and an evaporation number of larger than 100; esters of saturated and unsaturated fatty~acids with C13 to C30 chains. in particular esters of phthalic acid, adipic acid, sebatic acid, oleic acid and linolenic acid; mixtures of the aforementioned esters with alcohols, such as methanol, ethanol, butanol, glycerine, glycol, ethylhexanols, octyl alcohol and fatty alcohols such as those produced from the aforementioned fatty—acids; esters of phosphoric acid with C4-C13 alcohols; phenolsulphonic acid ester; and silicone oils with a molecular mass of between 100 and 10,000 atomic mass units.

3. A process as claimed in Claim 2 characterised in that the coating agent is a polyglycol material.

4. A process as claimed in Claim 1 or Claim 2 characterised in that the adhesive components may be selected from : starch, and/or cellulose or a derivative thereof, such as methyl cellulose, or in the case of a cement based adhesive the adhesive components are selected from: cement, silica and a cellulose, such as methyl cellulose.

5. A process as claimed in any preceding claim wherein the adhesive composition further comprises a clay component, such as china clay.

6. A process as claimed in Claim 5 characterised in that the clay component comprises up to 25% by weight of adhesive prior to its addition to water or other suitable carrier.

7. An adhesive composition, particularly suitable as a wallpaper or poster adhesive, characterised in that the adhesive composition in powder form is substantially dust-free and comprises starch, and/or a cellulose or cellulose derivative such as a methyl cellulose, and a coating agent selected from: polyglycols, for example polyethyleneglycol or polypropyleneglycol; polyetherpolyols of a molecular mass of between 100 and 6000 atomic mass units particularly those based on the aforementioned polyglycols, carbohydrates based on paraffin oil or aromatic and naphthenic oils and terpenes with a boiling point of greater than 2000C and an evaporation number of larger than 100; esters of saturated and unsaturated fatty—acids with C13 to C30 chains, in particular esters of phthalic acid, adipic acid. sebatic acid, oleic acid and linolenic acid; mixtures of the aforementioned esters with alcohols, such as methanol, ethanol, butanol, glycerine, glycol, ethylhexanols, octyl alcohol and fatty alcohols such as those produced from the aforementioned fatty—acids; esters of phosphoric acid with C4-CH,» alcohols; phenolsulphonic acid ester; and silicone oils with a molecular mass of between 100 and 10,000 atomic mass units.

8. An adhesive composition comprising at least one adhesive component selected from a starch and/or cellulose or a derivative thereof, or in the case of a tile adhesive or grout, selected from cement, silica, and a cellulose or cellulose derivative, characterised in that the adhesive component(s) are sprayed with a coating agent selected from: polyglycols, for example polyethyleneglycol or polypropyleneglycol; polyetherpolyols of a molecular mass‘ of between 100 and 6000 atomic mass units based on the aforementioned polyglycolsi; carbohydrates based on paraffin oil or aromatic and naphthenic oils and terpenes with a boiling point of greater than 200°C and an evaporation number of larger than 100; esters of saturated and unsaturated fatty-acids with C13 to C20 chains, in particular esters of phthalic acid, adipic acid, sebatic acid, oleic acid and linolenic acid; mixtures of the aforementioned esters with alcohols, such as methanol, ethanol, butanol, glycerine, glycol, ethylhexanols, octyl alcohol and fatty alcohols such as those produced from the aforementioned fatty-acids; esters of phosphoric acid with C4-C18 alcohols: phenolsulphonic acid ester; and silicone oils with a molecular mass of between 100 and 10,000 atomic mass units such that the composition is substantially dust free.

9. An adhesive composition according to claim 7 or claim 8 further comprising a clay component, such as china clay.

10. An adhesive composition as claimed in Claim 9 characterised in that the clay component comprises up to 25% by weight of the adhesive prior to its addition to water or other suitable carrier.

11. A process as claimed in Claim 1 substantially as described herein with reference to the Examples.

12. A dust—free adhesive powder composition whenever prepared by a process as claimed in any ofClaims l to 5 or 11.

13. An adhesive composition, as claimed in any of Claims 7 to 10, substantially as described herein with reference to the Examples. '