IES62632B2 - Process for producing adhesives - Google Patents

Abstract

A process for the production of a substantially dust-free adhesive power composition is described. The process comprises admixing adhesive component(s) in dry powder form to produce a homogeneous adhesive composition, and spraying a coating agent, in the form of a fine mist, onto the adhesive component(s) during the mixing step to bind dust particles present in the dry powder mixture. The invention also concerns to adhesive composition made by the 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. It also enables the use of Chinaclay in the composition.

Description

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 or 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.

Background Art It has been known to formulate wallpaper adhesives using starch, cellulose derivatives or methyl cellulose either in their pure forms or in combination others 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 as this adhesive is subject to fungus growth. - 2 Cellulose derivative based adhesives exhibits 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 -t water absorption. The salt also corrodes wallpaper adhesive application machines. Pure saltfree 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 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.

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 -i compositions.

Summary of the Invention Accordingly, the invention provides a process for the production of a substantially dust-free adhesive power composition which comprises admixing the adhesive component(s) 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 composition 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: polvglycols, for example polyethvlenglycol or polypropylenglvcol; polyetherpolvoles of a molecular mass of between 100 and 5000 atomic mass units based on the aforementioned polyglycols,· carbonhvdrates based on paraffin oil or aromatic and naphtenic 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 fattv-acids with to C2Q 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, ethvlhexanols, octyl alcohol and fat alcohols such as those produced from the aforementioned fattv-acids; esters of phosphoric acid with C^-C^g alcohols; phenolsulphonicacid 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 component(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: - 5 Example 1 - Wallpaper Adhesive - 100% Starch 0-100% CMC - 20% Chinaclay - 10% Coating fluid Example A.

Comparative Example of Conventional Wallpaper Adhesive - 100% Starch - 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 10 - 40%.

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

Claims (5)

1. A process for the production of a substantially dust-free adhesive power composition which comprises admixing the 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 polvetherpolyoles of a molecular mass of between 100 and 6000 atomic mass units based on the aforementioned polvglycols, carbonhydrates based on paraffin oil or aromatic and naphtenic 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 fattv-acids with C·^ to C20 c ^ ains » 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 fat alcohols such as those produced from the aforementioned fatty-acids; esters of phosphoric acid with C4-C18 alcohols; phenolsulphonicacid ester and silicone oils with a molecular mass of between 100 and 10,000 atomic mass units.

3. 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 and/or a clay component, such as China clay, or in the case of a cement based adhesive the adhesive components are selected from: cement, silica and a cellulose, such as methyl cellulose.

4. 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, a cellulose or cellulose derivative such as a methyl cellulose, a clay component such as China clay, and a coating agent as defined in Claim 2.

5. 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 5 in that the adhesive component(s) are sprayed with a coating agent as defined in Claim 2 such that the composition is substantially dust free.