Abrasive tool making process – material – or composition – Miscellaneous
Patent
1988-05-05
1989-05-23
Lieberman, Paul
Abrasive tool making process, material, or composition
Miscellaneous
51295, 51298, 51320, B24D 300
Patent
active
048327069
DESCRIPTION:
BRIEF SUMMARY
The invention relates to abrasive media for use in removing paint, mould flash or the like from articles. The media comprises abrasive particles which may be contacted with the article to be treated as a suspension in a liquid carrier using a water slurry by a process known as wet blasting or in a high pressure stream of gas e.g. air by a process known as dry blasting.
U.S. Pat. No. 3,410,124, published in 1968, discloses a shot blasting process in which articles are blasted with an aqueous slurry containing particles of synthetic resin which particles are round edged, elastic, non softening and hard. The particles may be made from a variety of synthetic resins including urea formaldehyde.
U.S. Pat. Nos. 4,545,155 and 4,548,617, both published in 1985, disclose the use of particles of synthetic resin to remove mould flash. The particles are applied in a slurry of water containing a surfactant. The particles may be made from a variety of synthetic resins, including thermoset resins.
GB Pat. No. -A-1571239, published in 1980, discloses the use of particles of silica sand and slag for removing rust from articles by dry blasting, which particles are first coated with a thermoset resin so that the particles will have increased strength and less dust will be generated. The coating may be provided by a variety of thermoset resins, and urea furfuryl alcohol formaldehyde resin is mentioned.
In dry blasting it is also known to use crushed coconut shells or polystyrene granules as abrasive media. These materials are insufficiently hard for effective abrasion and/or are of low impact strength. It is also known to use crushed amino plastics moulding waste (in which filler is present) as abrasive media but this material lacks resistance to breakdown. It is further known to consolidate an amino plastics moulding powder incorporating a filler such as wood flour or cellulose fibre into shapes which are subsequently comminuted to yield media particles of suitable sizes. This method is expensive.
The invention is based on the realisation that particles of cured urea formaldehyde furan resin can be used with advantage as abrasive media, in wet or dry blasting or similar processes for abrasive treatment.
In one aspect, the invention provides a method of treating the surface of an article comprising contacting the surface to be treated with abrasive particles characterised in that the abrasive particles are of set urea formaldehyde furan resin.
The particles are hard, angular and sharp-edged; they have a degree of toughness and resilience which makes them resistant to breakdown in use e.g. total disintegration on impact. The particles can be free-flowing for handling in dry blasting.
According to another aspect of the invention there is provided a method of forming abrasive particles of the invention, comprising curing a liquid urea formaldehyde furan resin to translucent and homogeneous form, and comminuting the resin to yield particles of predetermined shape.
In a preferred feature, a liquid urea formaldehyde furan resin is made and poured into a mould and then set using an acid catalyst selected so that the liquid first gels to a rubbery condition; the rubbery moulding is removed and cut into shapes which are allowed to dry and cure such that extensive cracking occurs to provide on breakage highly angular chips which are then comminuted to the desired particle size.
The resin may have a urea:formaldehyde ratio of from 1:1.3 to 1:2.5, preferably 1:1.6 to 1:1.9 and may be prepared by a one-, or preferably two-, stage process. In the two-stage process urea and formaldehyde are preferably initially polymerised at a ratio of about 1:2.2 under acidic conditions, the mixture then neutralised, urea added to bring the ratio to 1:1.6 to 1:1.9 and polymerisation then continued to give a resin of solids content in the range of about 55 to about 75% with a corresponding viscosity of about 2 to about 20 c.Poise at 25.degree. C. More preferably the solids content is from 60 to 65% and the viscosity from 3 to 10 c.Poise.
The urea and formal
REFERENCES:
patent: 3410124 (1968-11-01), Sowa
patent: 4545155 (1985-10-01), Nakata
patent: 4548617 (1985-10-01), Miyatani et al.
patent: 4575396 (1986-03-01), Matsumoto et al.
patent: 4666465 (1987-05-01), Matsumoto et al.
patent: 4731125 (1988-03-01), Carr
International Limited
Lieberman Paul
Thompson Willie J.
Unicorn Industries Public Limited Company
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