CA1094332A - Sand blasting abrasive materials and method of producing the same - Google Patents
Sand blasting abrasive materials and method of producing the sameInfo
- Publication number
- CA1094332A CA1094332A CA285,000A CA285000A CA1094332A CA 1094332 A CA1094332 A CA 1094332A CA 285000 A CA285000 A CA 285000A CA 1094332 A CA1094332 A CA 1094332A
- Authority
- CA
- Canada
- Prior art keywords
- abrasive material
- resin
- particles
- coating
- sand
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Polishing Bodies And Polishing Tools (AREA)
Abstract
SAND BLASTING ABRASIVE MATERIALS AND
METHOD OF PRODUCING THE SAME
ABSTRACTOF THE DISCLOSURE
Method of producing abrasive materials suitable for sand blasting, and the materials so produced, consisting of silica sand and/or slag, coated with a thermosetting resin by heat treatment, and the coating being then rendered insoluble and unmeltable, by subsequent heat treatment. The resin may contain a catalyst.
METHOD OF PRODUCING THE SAME
ABSTRACTOF THE DISCLOSURE
Method of producing abrasive materials suitable for sand blasting, and the materials so produced, consisting of silica sand and/or slag, coated with a thermosetting resin by heat treatment, and the coating being then rendered insoluble and unmeltable, by subsequent heat treatment. The resin may contain a catalyst.
Description
~ 3 3 ~
The abrasive material blastin~ mdchine used in the sand ~lasting process i8 designed to blast particles o~ a~raslv~
against a surface to be cleaned, the impact produced being e~ective to remove rust and the like from the surface.
As for the abrasive materials~ silica sand and slag are chiefly used. However9 silica sand and s~ag are brittle and generally have many cracks in their surfaces~ so that upon striking the surface to be clec~ned, th~y breaX into fine pieces, producing a large amount of dust. Therefore, the blast clec~ning operation~ if carried out in the open air, would greatl~ i~fluence the nearby housing environment, forming a cause of enviro~mental pollution. ~here is another serious problem, nc~mely th~t tha health of the workers who inhale such dust is endangered.
An object of the present inven-tion is to prevent the occurrence of environmental pollution du~ to such du~t and to co~tribute ~o the improvement of wor~cing environme~tal condi-tions, by coating ~n a~rasive material with a thermosettir.g resi~ which i~ re~dered in901uble and infusible, whereby the strength o~ the abrasive material, which may be ~ilica sand or slag, is increased. ~hus, particulc~rly in the case of s~lica sand~ which has many cracks~ the resin penetrates even ~o the in~ermost areas o~ the cr~cks, the~eby increasi~g the impac~ resistance of silica sand.
According to the i~vention5 the presence of the thermosetting re~in coating ~hat is insoluble and infusible increases the ef~iciency o~ blast cleaning operatio~ which u~eq an abra~ive material. Mor~ particularly, when sand blasting abrasive mate-rial is blown agalnst a surface to be cleaned, said abrasive material will, , . . . .
.
~i, ~43~
0~ course, obtain the heat generated by the impact. In this case, in the present invention, the the~mosetting resin coating, rendered insoluble and infusible, on the abrasive material is not melted by the heat of impact; rather it further sets to thereby improve the blast cleaning efficiency.
The present invention, then, in one aspect, resides in an.abrasive material for sand blasting., con-sisting essentially of a.material selected from the group that consists of silica sand and slag, and a heat-treated coating thereon Qf a thermosetting resin (other than epoxy resins), said coating containing a setting catalyst, and being insoluble and infusible on effect of re-applied heat, said coated abrasive material being in the form o~ fine, ~ree flowing discrete particles, a:nd said abrasive material being urther characterized by having a higher degree of uniformity with respect to particle size, than conventional abrasive material~ and in that a greater proportion of the abrasive particles are re-usable than is the case with conventional abrasive materials; said coating increasing the strength of the abrasive materialby pene-trating into.cracks inherent in the abrasive material so that a substantial proportion o~ the pulveriæed abrasive ::
material can be recovered ater the sand blasting for re-- use; whereby the heat, generated by.impact when ~he abrasive material is blow~ against a surface to be.cleaned by the sand blasting, leaves the insoluble and infusible coating in this state, and actually continues the setting of that coating so that sand-blasting efficiency is increased;
and whereby dust formation during the sand blasting is reduced, thereby increasing environmental protection.
33~2 In another aspect, the present invention resides in a method of producing abrasive materials for sand blasting, comprising the steps of: carrying out a first phase by adding a thermosetting resin, to which a se~ting catalyst has been added to a material selected from .... ~
the group consisting o~ silica sand and slag; mixing particles of said abrasive material with said resin while blowing heated air thereinto so as to independently coat tha par~icles o~ the resulting-sand-blasting abrasive material with the resin without causing coalescence of the particles;
and carrying out a s~cond, separate phase by re-heating the coated abrasive particles to a temperature-of about 300C;
said temperature beiny higher than that employed in the first phase, while effecting stirring o~ said particles by means of a heated gas stream or by means o~ a vibration producing device so as to render the resin coating on the abrasive material insoluble and inusible whi~e at the same time leaving the-coated abrasive material in a powdered condition.
~~ The present invention will now be described in more detail with reference to the accompanying drawings, in which;
Fig. 1 is a schematic view of an apparatus for produc-ing sand blasting abrasive materials according to an embodiment of the invention;
Fig. 2 is a schematic view of the principal portion of another embodiment of the invention; and Fig. 3 and 4 are particle size distribution comparison test graphs showing the data of comparative tests between the pres-ent invention and the pxior art.
- 3a -f ~
l i I
3~ ) Re~erring to ~ig. 1~ a material t.an~ 'i containi~ iliea sand (or ~lag) is adapted ~o supply t~e silica sand (or slag) to a measuring tank 2 by openi~g an outlet damper 1a disposed in th~ lower region o~ said material tank 10 After a predetermined amount o~ s~lica sand (or slag) is measured b~
said measurin~ tank 2, it is dumped~ nto a mixer 3 di~posed below the measuring ta~k, Also charged- in~o said miæer 3 i8 a setting catalyst in a fixed prnportion to a thermosetting r sin to be presen~l~ described, a~d said ~ilica sand and ~etting catalyst are uniformly mixed for about one mixlute, whereupon a thermo~
set~ing resin i~ a fixed proportion to the silica sand is charged into the mixer 3 and9 w~ blowing hot air at 80~100~C
from a hot air blower 4 into the mixer, they are mixed for about five minutes. As a result, the particles of silica ~and have a thermosetting resin coating of fixed ~hickness ~ormed on their surfaces and such coatings are dried a:nd set by the action of heat.
The described mixing ~ddin~ resin to the sand or slag) and blowing heated air thereinto can be.defined as a ~irst phase of the invent-- ive process.
The amount~ of ~aid thermosetting re in and setti~g catal~st ma~ be ~uitabl;~ ch ~ gPd accordi ~ to the prope:r~ties of ~h~ ~ilica sand o:r sla~ used. ~s an èxample, in the.case of No. 4 silica sand specified in the Japanese Industrial Standards (JI~)j 2 parts o~ thermos~tting resin and 1 part of set~ing catal~st are used wi~h respect to 100 parts of ~o. 4 silica sand. As for slag~
proportion~ similar to those described may be used. By the pro~ess described above 9 the particles of silica sand or slag are coa~ed with said thermosetting resin independently without the p~Fticles sticki~g to each other to ~orm a lump or l~nps. In this 3~ case~ since hot air is supplied duri~g the mixing, the thermo-settin3 resin undergoes a chemical change which renders it insoluble and infusible to some exte~t. When slag is used, ;3 32 howe~er, the resin on the particles of slag become~ viscous like glue and the viscous condition of the resin lasts longer than in the case of silica sand~ making it somewhat difficult to achieve the thermal setting thereof. ~hus, in order to ma~e the thermal setting complete and also, in the case of silica sand, to cause the resin, which has penetrated even to the innermost areas of crack~ peculiar to silica sand, to thermally set complete~y, the silica sa d or slag mixed a~d resin-coated:.in the prec~ding process is heat treated again.
10More particularly, the stirred silica sand ~or.slag~
reference hereinafter being made to silica sand) i~ charged into a hopper 5 and then the treated silica sand flowing out of the bo~tom o~ said hopper 5 is received on a con~eyor 6 for -transport to a rotar~ kiln 7. ~his arrangement for receiving the silica sand from th~ mixe~ 3 and then transporting it b~ the conveyor 6 i~ intended to adaust the rate of supply of silica sand to the rotar~ kiln 7 according to the capacit~ of the latter. On the exit side of ~he rotar~ kiln 7, oul;let ports 8 suitably : spaced apart are formed in the outer peripheral surface of the rotar~ kiln 7 and hot gas at about 3OOC is blown into the rotary kiln 7 from the exit of the latter, said hot gas travel-ing toward the entrance of the rotary kiln and being finall~
expelled into the atmosphere b~ an exhaust fan 9~ As for said ho~ gas, air heated b~ waste gas resulting ~rom combustion of kerosene or tha like is used a~d is blown intolthe rotary kiln 7 by a nozzle 10. A:s is. known in the art, the rotar;y kiln 7 ha~
annular rails 11 mounted thereon at a plurality of ~uitable places and each annular rail 11 is supported by a pair of rollers 12. I~ this way, the rotary kiln 7 i9 rotatably supported on a support base 13. ~esignated at 14 is a drive~ gear wheel ~ixed on the outer peripheral surface of the rotary kiln 7 and meshing ~r ~ .~
33~
with a drive gear wheel 16 secured to a motor 15, whereb~ the rota.ry kiln 7 i~ rotated around it~ own axis in o~e direction.
Designated at 17 are support roller~ each abutting against thë iatera surface o~ the associated annular rail 11. I~hile each support roller 17 i3 shown located above the associated support rollers 12 for simplicit~ of illustration onl~, actually it is located betwee~ and above the level of the associated support rolier~
17. ~he suppo~t roller~ 17 serve to preve~ the rotar~ kil~
:~ 7 from inadverte~tly sliding in the direction o~ incli~ation thereo~. ~he rotary kiln 7 is internally provided with a plurality o~ stirring vanes 18 extendi~g from the entrance to th~ middle of the le~gth o~ th0 rotary kiln 7. Accordi~gl~g with the ro~ary kiln 7 being rotated around its own axis and w.ith heated air being blown thereinto, if silica sand transported b~ the conve~or 6 is supplied to the rotary kiln 7 through a chute 199 the silica sand ls repeatedl~ sub~ected to ~the ac~ion of the stirring vanes 18 scooping it and the~ ~
dropping it with the rota~ion of th~ rotary ~iln 7 around its own axis and durin~ thi3 action it comes in contact with the ho~ gas, whereb~ the ~hermosetting resin coatings on the particles of silica sand undergo a final thermosetting chemical chanae to be rendered insoluble and infusible. The above-described repeated heating while stirring can be defined as a second, separate phase of the invention. The silica sand passing by the stirring vanes 18 flows inside the rotary kiln while being shaken or vibrated until it reaches the exit side of the rotary kiln 7 and finally flows out through the outlat ports 8. In this connection, it is to be noted that a vibration conveyor 30 shown in Fig. 2 may be used as a heat-ing and stirring means in place of the rotary kiln 7 shown in l~
.. .. .
.
~ 3 3 ~
?ig. 1. More particularl~, the vibration conve~or 30 supported b~ springs 32 a~d adapted to be vibrated b~ vibra~ion means 33 such as an eccentri.c motor is associated with infrared ray radiating devices 3~1 locatsd thereabo~e 9 SO that while the silica ~and supplied to.the conveyor 30 from the conveyor 6 through the chute 19 shown in Fig. ~ is being vibrated a~d transported b~ the conveyor 30, it is heated b~ the infrared ray radiating de~iceR 31 so as to render the thermosetting resin coatings in901uble and ln~usible. Re~erring bac~ to Fig. 1, the silica ~and particles which have been discharged ~rom the rotary kiln 7 are collected at the lower end of a buc~et lifter 21 ~ a chute 20. The particles thus collected are then lifted b~ the bucket li~ter 21 operated b~ a motor 22 and are supplied into 8 hopper 24 disposed in a ~orting tower 23. Disposed inclined below hopper 2~ is a wire scree~ 25 having the required mesh, and vibrating means 26 is provided for vibrating the wire screen 25. Desi~nated at 27 are springs ~or supporting the wire screen 25. 0~ the silica sand particles flowing down the hopper 2~ onto the wire screen 25~'onl~
thos`e having particle sizes below a certain limit are allowed to pass through the wire screen 25 under the action of the vibrations imparted thereto while the othe~ having sizes above said limit flow down o~ said wire screen 25 and are discharged into the outside of the ~stem. Those passing through the wire screen 25 are then transported by a conve~or 28 to a product storage tank. Designated at 29 is an exhaust fan serving to discharge cool air which is being admitted into the sorting tower 23 ~rom below, whereb~ the silica sand which was at about 110C when leaving the rotar~
kiln 7 or vibration conve~or 30 is cooled to about 80-50C. ~he time required for the silica sand to pass through the rotary kiln 7 or vibration con~e~or 30 is suitabl~ about 1 minute and 30 seconds. If the mesh size of the wire screen 25 is changed, the particle size of silica sand which can be sorted will differ.
Thus, it is convenient to prepare a plurality of wire screens having different mesh sizes so that they may be selectively used.
The thermosetting resins available for the present invention include phenolic resins, urea resins, melamine resins, polyester resins, and alkyd resins. As an example, such a resin ; is prepared by deriving furfural from pentose which is extracted from t~e stalks of cone or kaoliang, adding hydrogen to said furfural to provide furfuryl alcohol, and denaturing the latter with a phenol.
, `~
7a~
~''3~33~
.
,! -) .
Generally, mention may be made of those resins which are commercially available undex the name of urea-furfur~l alcohol formaldehyde resins and of phenol furfur~l alcohol fo~maldehyde resins.
: As for setting catalysts~ it is desirable to use phosphate typo catalysts such as an aqueous solution of phosphoric acid (75% concentration) or sulfate t~pe catalysts such as an aqueous solution of sulfuric acid (~0~ concentration~, ~he effect~ of the abrasive materials prepared according to .10 the present i~vsntion used for blast cleaning are shown b~low by way of example in comparison with conventional abTasi~e materials for blast cleaning"
~1) Result of Comparati~e ~est for Amount of Dust Abra~ive Matt~rial Used . Amount of Dust No. 4 silica sand.(JIS, conventional) 361 mg/m~
No. 4 silica sand resin-coated acco~ding to the invention 22 mg/m3 Slag (conventional) 1~,2 mg/m3 ~lag resin-coated according to 20 the in~ention 11,3 mg/m3 ~ he above result was obtained by measuring ~he amount of dust (in mg~ per 1 m~ at a location 11 m do~mstream of the site for te~t~ ~here an abrasive material was blown against a sur~ace to be cleaned,
The abrasive material blastin~ mdchine used in the sand ~lasting process i8 designed to blast particles o~ a~raslv~
against a surface to be cleaned, the impact produced being e~ective to remove rust and the like from the surface.
As for the abrasive materials~ silica sand and slag are chiefly used. However9 silica sand and s~ag are brittle and generally have many cracks in their surfaces~ so that upon striking the surface to be clec~ned, th~y breaX into fine pieces, producing a large amount of dust. Therefore, the blast clec~ning operation~ if carried out in the open air, would greatl~ i~fluence the nearby housing environment, forming a cause of enviro~mental pollution. ~here is another serious problem, nc~mely th~t tha health of the workers who inhale such dust is endangered.
An object of the present inven-tion is to prevent the occurrence of environmental pollution du~ to such du~t and to co~tribute ~o the improvement of wor~cing environme~tal condi-tions, by coating ~n a~rasive material with a thermosettir.g resi~ which i~ re~dered in901uble and infusible, whereby the strength o~ the abrasive material, which may be ~ilica sand or slag, is increased. ~hus, particulc~rly in the case of s~lica sand~ which has many cracks~ the resin penetrates even ~o the in~ermost areas o~ the cr~cks, the~eby increasi~g the impac~ resistance of silica sand.
According to the i~vention5 the presence of the thermosetting re~in coating ~hat is insoluble and infusible increases the ef~iciency o~ blast cleaning operatio~ which u~eq an abra~ive material. Mor~ particularly, when sand blasting abrasive mate-rial is blown agalnst a surface to be cleaned, said abrasive material will, , . . . .
.
~i, ~43~
0~ course, obtain the heat generated by the impact. In this case, in the present invention, the the~mosetting resin coating, rendered insoluble and infusible, on the abrasive material is not melted by the heat of impact; rather it further sets to thereby improve the blast cleaning efficiency.
The present invention, then, in one aspect, resides in an.abrasive material for sand blasting., con-sisting essentially of a.material selected from the group that consists of silica sand and slag, and a heat-treated coating thereon Qf a thermosetting resin (other than epoxy resins), said coating containing a setting catalyst, and being insoluble and infusible on effect of re-applied heat, said coated abrasive material being in the form o~ fine, ~ree flowing discrete particles, a:nd said abrasive material being urther characterized by having a higher degree of uniformity with respect to particle size, than conventional abrasive material~ and in that a greater proportion of the abrasive particles are re-usable than is the case with conventional abrasive materials; said coating increasing the strength of the abrasive materialby pene-trating into.cracks inherent in the abrasive material so that a substantial proportion o~ the pulveriæed abrasive ::
material can be recovered ater the sand blasting for re-- use; whereby the heat, generated by.impact when ~he abrasive material is blow~ against a surface to be.cleaned by the sand blasting, leaves the insoluble and infusible coating in this state, and actually continues the setting of that coating so that sand-blasting efficiency is increased;
and whereby dust formation during the sand blasting is reduced, thereby increasing environmental protection.
33~2 In another aspect, the present invention resides in a method of producing abrasive materials for sand blasting, comprising the steps of: carrying out a first phase by adding a thermosetting resin, to which a se~ting catalyst has been added to a material selected from .... ~
the group consisting o~ silica sand and slag; mixing particles of said abrasive material with said resin while blowing heated air thereinto so as to independently coat tha par~icles o~ the resulting-sand-blasting abrasive material with the resin without causing coalescence of the particles;
and carrying out a s~cond, separate phase by re-heating the coated abrasive particles to a temperature-of about 300C;
said temperature beiny higher than that employed in the first phase, while effecting stirring o~ said particles by means of a heated gas stream or by means o~ a vibration producing device so as to render the resin coating on the abrasive material insoluble and inusible whi~e at the same time leaving the-coated abrasive material in a powdered condition.
~~ The present invention will now be described in more detail with reference to the accompanying drawings, in which;
Fig. 1 is a schematic view of an apparatus for produc-ing sand blasting abrasive materials according to an embodiment of the invention;
Fig. 2 is a schematic view of the principal portion of another embodiment of the invention; and Fig. 3 and 4 are particle size distribution comparison test graphs showing the data of comparative tests between the pres-ent invention and the pxior art.
- 3a -f ~
l i I
3~ ) Re~erring to ~ig. 1~ a material t.an~ 'i containi~ iliea sand (or ~lag) is adapted ~o supply t~e silica sand (or slag) to a measuring tank 2 by openi~g an outlet damper 1a disposed in th~ lower region o~ said material tank 10 After a predetermined amount o~ s~lica sand (or slag) is measured b~
said measurin~ tank 2, it is dumped~ nto a mixer 3 di~posed below the measuring ta~k, Also charged- in~o said miæer 3 i8 a setting catalyst in a fixed prnportion to a thermosetting r sin to be presen~l~ described, a~d said ~ilica sand and ~etting catalyst are uniformly mixed for about one mixlute, whereupon a thermo~
set~ing resin i~ a fixed proportion to the silica sand is charged into the mixer 3 and9 w~ blowing hot air at 80~100~C
from a hot air blower 4 into the mixer, they are mixed for about five minutes. As a result, the particles of silica ~and have a thermosetting resin coating of fixed ~hickness ~ormed on their surfaces and such coatings are dried a:nd set by the action of heat.
The described mixing ~ddin~ resin to the sand or slag) and blowing heated air thereinto can be.defined as a ~irst phase of the invent-- ive process.
The amount~ of ~aid thermosetting re in and setti~g catal~st ma~ be ~uitabl;~ ch ~ gPd accordi ~ to the prope:r~ties of ~h~ ~ilica sand o:r sla~ used. ~s an èxample, in the.case of No. 4 silica sand specified in the Japanese Industrial Standards (JI~)j 2 parts o~ thermos~tting resin and 1 part of set~ing catal~st are used wi~h respect to 100 parts of ~o. 4 silica sand. As for slag~
proportion~ similar to those described may be used. By the pro~ess described above 9 the particles of silica sand or slag are coa~ed with said thermosetting resin independently without the p~Fticles sticki~g to each other to ~orm a lump or l~nps. In this 3~ case~ since hot air is supplied duri~g the mixing, the thermo-settin3 resin undergoes a chemical change which renders it insoluble and infusible to some exte~t. When slag is used, ;3 32 howe~er, the resin on the particles of slag become~ viscous like glue and the viscous condition of the resin lasts longer than in the case of silica sand~ making it somewhat difficult to achieve the thermal setting thereof. ~hus, in order to ma~e the thermal setting complete and also, in the case of silica sand, to cause the resin, which has penetrated even to the innermost areas of crack~ peculiar to silica sand, to thermally set complete~y, the silica sa d or slag mixed a~d resin-coated:.in the prec~ding process is heat treated again.
10More particularly, the stirred silica sand ~or.slag~
reference hereinafter being made to silica sand) i~ charged into a hopper 5 and then the treated silica sand flowing out of the bo~tom o~ said hopper 5 is received on a con~eyor 6 for -transport to a rotar~ kiln 7. ~his arrangement for receiving the silica sand from th~ mixe~ 3 and then transporting it b~ the conveyor 6 i~ intended to adaust the rate of supply of silica sand to the rotar~ kiln 7 according to the capacit~ of the latter. On the exit side of ~he rotar~ kiln 7, oul;let ports 8 suitably : spaced apart are formed in the outer peripheral surface of the rotar~ kiln 7 and hot gas at about 3OOC is blown into the rotary kiln 7 from the exit of the latter, said hot gas travel-ing toward the entrance of the rotary kiln and being finall~
expelled into the atmosphere b~ an exhaust fan 9~ As for said ho~ gas, air heated b~ waste gas resulting ~rom combustion of kerosene or tha like is used a~d is blown intolthe rotary kiln 7 by a nozzle 10. A:s is. known in the art, the rotar;y kiln 7 ha~
annular rails 11 mounted thereon at a plurality of ~uitable places and each annular rail 11 is supported by a pair of rollers 12. I~ this way, the rotary kiln 7 i9 rotatably supported on a support base 13. ~esignated at 14 is a drive~ gear wheel ~ixed on the outer peripheral surface of the rotary kiln 7 and meshing ~r ~ .~
33~
with a drive gear wheel 16 secured to a motor 15, whereb~ the rota.ry kiln 7 i~ rotated around it~ own axis in o~e direction.
Designated at 17 are support roller~ each abutting against thë iatera surface o~ the associated annular rail 11. I~hile each support roller 17 i3 shown located above the associated support rollers 12 for simplicit~ of illustration onl~, actually it is located betwee~ and above the level of the associated support rolier~
17. ~he suppo~t roller~ 17 serve to preve~ the rotar~ kil~
:~ 7 from inadverte~tly sliding in the direction o~ incli~ation thereo~. ~he rotary kiln 7 is internally provided with a plurality o~ stirring vanes 18 extendi~g from the entrance to th~ middle of the le~gth o~ th0 rotary kiln 7. Accordi~gl~g with the ro~ary kiln 7 being rotated around its own axis and w.ith heated air being blown thereinto, if silica sand transported b~ the conve~or 6 is supplied to the rotary kiln 7 through a chute 199 the silica sand ls repeatedl~ sub~ected to ~the ac~ion of the stirring vanes 18 scooping it and the~ ~
dropping it with the rota~ion of th~ rotary ~iln 7 around its own axis and durin~ thi3 action it comes in contact with the ho~ gas, whereb~ the ~hermosetting resin coatings on the particles of silica sand undergo a final thermosetting chemical chanae to be rendered insoluble and infusible. The above-described repeated heating while stirring can be defined as a second, separate phase of the invention. The silica sand passing by the stirring vanes 18 flows inside the rotary kiln while being shaken or vibrated until it reaches the exit side of the rotary kiln 7 and finally flows out through the outlat ports 8. In this connection, it is to be noted that a vibration conveyor 30 shown in Fig. 2 may be used as a heat-ing and stirring means in place of the rotary kiln 7 shown in l~
.. .. .
.
~ 3 3 ~
?ig. 1. More particularl~, the vibration conve~or 30 supported b~ springs 32 a~d adapted to be vibrated b~ vibra~ion means 33 such as an eccentri.c motor is associated with infrared ray radiating devices 3~1 locatsd thereabo~e 9 SO that while the silica ~and supplied to.the conveyor 30 from the conveyor 6 through the chute 19 shown in Fig. ~ is being vibrated a~d transported b~ the conveyor 30, it is heated b~ the infrared ray radiating de~iceR 31 so as to render the thermosetting resin coatings in901uble and ln~usible. Re~erring bac~ to Fig. 1, the silica ~and particles which have been discharged ~rom the rotary kiln 7 are collected at the lower end of a buc~et lifter 21 ~ a chute 20. The particles thus collected are then lifted b~ the bucket li~ter 21 operated b~ a motor 22 and are supplied into 8 hopper 24 disposed in a ~orting tower 23. Disposed inclined below hopper 2~ is a wire scree~ 25 having the required mesh, and vibrating means 26 is provided for vibrating the wire screen 25. Desi~nated at 27 are springs ~or supporting the wire screen 25. 0~ the silica sand particles flowing down the hopper 2~ onto the wire screen 25~'onl~
thos`e having particle sizes below a certain limit are allowed to pass through the wire screen 25 under the action of the vibrations imparted thereto while the othe~ having sizes above said limit flow down o~ said wire screen 25 and are discharged into the outside of the ~stem. Those passing through the wire screen 25 are then transported by a conve~or 28 to a product storage tank. Designated at 29 is an exhaust fan serving to discharge cool air which is being admitted into the sorting tower 23 ~rom below, whereb~ the silica sand which was at about 110C when leaving the rotar~
kiln 7 or vibration conve~or 30 is cooled to about 80-50C. ~he time required for the silica sand to pass through the rotary kiln 7 or vibration con~e~or 30 is suitabl~ about 1 minute and 30 seconds. If the mesh size of the wire screen 25 is changed, the particle size of silica sand which can be sorted will differ.
Thus, it is convenient to prepare a plurality of wire screens having different mesh sizes so that they may be selectively used.
The thermosetting resins available for the present invention include phenolic resins, urea resins, melamine resins, polyester resins, and alkyd resins. As an example, such a resin ; is prepared by deriving furfural from pentose which is extracted from t~e stalks of cone or kaoliang, adding hydrogen to said furfural to provide furfuryl alcohol, and denaturing the latter with a phenol.
, `~
7a~
~''3~33~
.
,! -) .
Generally, mention may be made of those resins which are commercially available undex the name of urea-furfur~l alcohol formaldehyde resins and of phenol furfur~l alcohol fo~maldehyde resins.
: As for setting catalysts~ it is desirable to use phosphate typo catalysts such as an aqueous solution of phosphoric acid (75% concentration) or sulfate t~pe catalysts such as an aqueous solution of sulfuric acid (~0~ concentration~, ~he effect~ of the abrasive materials prepared according to .10 the present i~vsntion used for blast cleaning are shown b~low by way of example in comparison with conventional abTasi~e materials for blast cleaning"
~1) Result of Comparati~e ~est for Amount of Dust Abra~ive Matt~rial Used . Amount of Dust No. 4 silica sand.(JIS, conventional) 361 mg/m~
No. 4 silica sand resin-coated acco~ding to the invention 22 mg/m3 Slag (conventional) 1~,2 mg/m3 ~lag resin-coated according to 20 the in~ention 11,3 mg/m3 ~ he above result was obtained by measuring ~he amount of dust (in mg~ per 1 m~ at a location 11 m do~mstream of the site for te~t~ ~here an abrasive material was blown against a sur~ace to be cleaned,
(2) Result of Comparative ~est ~or Depth o~ Indentation~
~o~ 4 silica sand (JI~, con~e~tional) 95 No, 4 silica sand resin-coated according to the in~ention 104 33~
.
~lag (con~en~ional) 100 ~lag resin-coated according to the invention 118 ~
:~he above result wa~ obtai~ed b~ calculating the average of two blas~ing operatiQns against a surface to be cleaned.
~o~ 4 silica sand (JI~, con~e~tional) 95 No, 4 silica sand resin-coated according to the in~ention 104 33~
.
~lag (con~en~ional) 100 ~lag resin-coated according to the invention 118 ~
:~he above result wa~ obtai~ed b~ calculating the average of two blas~ing operatiQns against a surface to be cleaned.
(3) Result of Comparatire ~est for Particle Size Distribu tion - Fig. 3 shows the distribution o~ particle sizes o~ ~o~ 4 ;:silica sand (JIS, co~ventional) and No. 4 silica sand resi~-coated according t;o ~he in~ention a~ measured before and after each ma-terial is blasted once, the particle size ~in mm) bei~g plotted as~the abscissa and the percentage as the ordinate. According to thIs graph, it is seen that the distribution of particle si7es o~
No. 4 silica sand resin-coated (the present inventive article) be~o:re use, as indicated b~ curre I, is such that the paxticle size range oX ~.1 mm to 0.6 mm covers 93.2~ (13~ ~ 54~ + 26.2~), demonstrating that the particles are ver~ uniform in size, wherea3 i~ the case of ~o. 4 siliça sand (conven~ional ar~iole) indicated by curve II, the same pa~ticle size range covers 7~O~ (6~ ~ ~2 ~ 36i7~), showiD~ that there is a relatively large amount of varia-tion i~ particle size. Further, when the particle size distribution of the material af~er being used once i8 investigated as to pa~ticle size~ of not les~ than 0.3 mm capable of being re-used, it is see~
that in the case of the present inven~i~e article indicatsd by curve III, 68.8~ i~ re-usable, whereas in the conYentional a~ticle indicated b~ cur~re IV, onl;~ 39.~ is re-usable, It i~ also seen that the amoun~ of dust (pa:F~icle~ o~ not more than 0,2 mm) found a~ter single bl~sti~æ is 3001% with the present inventive article and ~a.g wi~h the conventio~a~ article~
_g_ ... . ., . , . , , _ , . .. . . . . . . . . .. .. ...... .. ..
33 ~
~ i~. 4 shows tke distribution of particle size~ of slag (conventional articlej and the same kind of' slag resin-coated according to the presen~ in~e~io~ as measured before and after each material is blasted once. The particle size ~in mm) before said bla~ti~ is indicated by curve I' for the present inve~tive article an~ by curve II' ~or the conventional article and the pa~ticle size (in mm) after said blasting is indicated b~ curves III' for the present in~entive article and by cur~e IY' ~or the con~entional article. ~he abscissa indicates the particle size and the ordinate indicates the percenta~e.
Accordi~g to this graph, it is seen that the particle si2es of not Ies~ tha~ 0.3 mm'after single blasting ~Jhich are capable of boing re-used cover 73.5% (3~ ~ 9.5% ~- 22.6% ~ 17.1%) with the present inventive article a~d 60.5% (2.1% ~ 6~ 15.8~ + 18.4~) with the conventio~al article. It iq also seen that the amount o~
~u~t (par~icles o~ not more than 0.2 mm) found after a sin~le blas~ing i~ 26~ with the present invention whereas it is 38.
with the conventional article.
~rom the comparative test ~esults described abo~e, it i~ seen that as ~hown in the item (1) the abras:ive mat~rials resin-coated according to the invention provide a rate o~ production o~ dust ~hich i much lower than that of the conventional ~rticles and that particularly in the ca~e o~ silica sand the inventio~
i~ capable of reducing it to about 1~14 of the co~entional value. This means that the invention preYents environmental pollutio~ and con~ributes much to the improveme~ of working en~ironme~tal condition~.
As is clear from the item (2~, the a~rasive materials resin-coatad according tG the in~ention provide a~ indentation , . .
33~
.
.?
depth which i3 no~ ~ery dif~erent ~rom or, rather, greater than that pro~ided b~ the conventio~al articles, demonstrating that the invention improves the blast cleaning effect.
: ~uxther, as is clear from the item (~), the abrasive materials according to the inventio~ retain ~ewer cracks than the conventional articles, so that a correspondingly greater proportion of used or blasted material can be recovered ~or re-use b~ installing an abrasive material recov-ering device, thus contributing much to the reductio~ o~ cost.
Fkrther,.:the presen~ inventive articles are also superior to the conventional articleAs i~ respect of reducing the amount o~ dust.
o11-. ~
.
No. 4 silica sand resin-coated (the present inventive article) be~o:re use, as indicated b~ curre I, is such that the paxticle size range oX ~.1 mm to 0.6 mm covers 93.2~ (13~ ~ 54~ + 26.2~), demonstrating that the particles are ver~ uniform in size, wherea3 i~ the case of ~o. 4 siliça sand (conven~ional ar~iole) indicated by curve II, the same pa~ticle size range covers 7~O~ (6~ ~ ~2 ~ 36i7~), showiD~ that there is a relatively large amount of varia-tion i~ particle size. Further, when the particle size distribution of the material af~er being used once i8 investigated as to pa~ticle size~ of not les~ than 0.3 mm capable of being re-used, it is see~
that in the case of the present inven~i~e article indicatsd by curve III, 68.8~ i~ re-usable, whereas in the conYentional a~ticle indicated b~ cur~re IV, onl;~ 39.~ is re-usable, It i~ also seen that the amoun~ of dust (pa:F~icle~ o~ not more than 0,2 mm) found a~ter single bl~sti~æ is 3001% with the present inventive article and ~a.g wi~h the conventio~a~ article~
_g_ ... . ., . , . , , _ , . .. . . . . . . . . .. .. ...... .. ..
33 ~
~ i~. 4 shows tke distribution of particle size~ of slag (conventional articlej and the same kind of' slag resin-coated according to the presen~ in~e~io~ as measured before and after each material is blasted once. The particle size ~in mm) before said bla~ti~ is indicated by curve I' for the present inve~tive article an~ by curve II' ~or the conventional article and the pa~ticle size (in mm) after said blasting is indicated b~ curves III' for the present in~entive article and by cur~e IY' ~or the con~entional article. ~he abscissa indicates the particle size and the ordinate indicates the percenta~e.
Accordi~g to this graph, it is seen that the particle si2es of not Ies~ tha~ 0.3 mm'after single blasting ~Jhich are capable of boing re-used cover 73.5% (3~ ~ 9.5% ~- 22.6% ~ 17.1%) with the present inventive article a~d 60.5% (2.1% ~ 6~ 15.8~ + 18.4~) with the conventio~al article. It iq also seen that the amount o~
~u~t (par~icles o~ not more than 0.2 mm) found after a sin~le blas~ing i~ 26~ with the present invention whereas it is 38.
with the conventional article.
~rom the comparative test ~esults described abo~e, it i~ seen that as ~hown in the item (1) the abras:ive mat~rials resin-coated according to the invention provide a rate o~ production o~ dust ~hich i much lower than that of the conventional ~rticles and that particularly in the ca~e o~ silica sand the inventio~
i~ capable of reducing it to about 1~14 of the co~entional value. This means that the invention preYents environmental pollutio~ and con~ributes much to the improveme~ of working en~ironme~tal condition~.
As is clear from the item (2~, the a~rasive materials resin-coatad according tG the in~ention provide a~ indentation , . .
33~
.
.?
depth which i3 no~ ~ery dif~erent ~rom or, rather, greater than that pro~ided b~ the conventio~al articles, demonstrating that the invention improves the blast cleaning effect.
: ~uxther, as is clear from the item (~), the abrasive materials according to the inventio~ retain ~ewer cracks than the conventional articles, so that a correspondingly greater proportion of used or blasted material can be recovered ~or re-use b~ installing an abrasive material recov-ering device, thus contributing much to the reductio~ o~ cost.
Fkrther,.:the presen~ inventive articles are also superior to the conventional articleAs i~ respect of reducing the amount o~ dust.
o11-. ~
.
Claims (7)
1. An abrasive material for sand blasting, con-sisting essentially of a material selected from the group that consists of silica sand and slag, and a heat-treated coating thereon of a thermosetting resin (other than epoxy resins), said coating containing a setting catalyst, and being insoluble and infusible on effect of re-applied heat.
said coated abrasive material being in the form of fine, free flowing discrete particles, and said abrasive material being further characterized by having a higher degree of uniformity with respect to particle size, than conventional abrasive material, and in that a greater proportion of the abrasive particles are re-usable than is the case with conventional abrasive materials; said coating increasing the strength of the abrasive materialby pene-trating into cracks inherent in the abrasive material so that a substantial proportion of the pulverized abrasive material can he recovered after the sand blasting for re-use; whereby the heat, generated by impact when the abrasive material is blown against a surface to be cleaned by the sand blasting, leaves the insoluble and infusible coating in this state, and actually continues the setting of that coating so that sand-blasting efficiency is increased;
and whereby dust formation during-the sand blasting is reduced, thereby increasing environmental protection.
said coated abrasive material being in the form of fine, free flowing discrete particles, and said abrasive material being further characterized by having a higher degree of uniformity with respect to particle size, than conventional abrasive material, and in that a greater proportion of the abrasive particles are re-usable than is the case with conventional abrasive materials; said coating increasing the strength of the abrasive materialby pene-trating into cracks inherent in the abrasive material so that a substantial proportion of the pulverized abrasive material can he recovered after the sand blasting for re-use; whereby the heat, generated by impact when the abrasive material is blown against a surface to be cleaned by the sand blasting, leaves the insoluble and infusible coating in this state, and actually continues the setting of that coating so that sand-blasting efficiency is increased;
and whereby dust formation during-the sand blasting is reduced, thereby increasing environmental protection.
2. An abrasive material according to claim 1 comprising 2 parts of the thermosetting resin and 1 part of setting catalyst with respect to 100 parts of No. 4 silica sand.
3. A method of producing abrasive materials for sand blasting, comprising the steps of: carrying out a first phase by adding a thermosetting resin, to which a setting catalyst has been added to a material selected from the group consisting of silica sand and slag; mixing particles of said abrasive material with said resin while blowing heated air thereinto so as to independently coat the particles of the resulting sand-blasting abrasive material with the resin without causing coalescence of the particles;
and carrying out a second, separate phase by re-heating the coated abrasive particles to a temperature of about 300°C;
said temperature being higher than that employed in the first phase, while effecting stirring of said particles by means of a heated gas stream or by means of a vibration producing device so as to render the resin coating on the abrasive material insoluble and infusible while at the same time leaving the coated abrasive material in a powdered condition.
and carrying out a second, separate phase by re-heating the coated abrasive particles to a temperature of about 300°C;
said temperature being higher than that employed in the first phase, while effecting stirring of said particles by means of a heated gas stream or by means of a vibration producing device so as to render the resin coating on the abrasive material insoluble and infusible while at the same time leaving the coated abrasive material in a powdered condition.
4. A method as set forth in Claim 3, wherein the step of rendering said thermosetting resin insoluble and infusible is performed by using a rotary kiln, wherein hot air at the required temperature is blown into said kiln from one end thereof.
5. A method as set forth in Claim 3, wherein the step of rendering said thermosetting resin insoluble and infusible is performed by using a vibration conveyor irradiated with infrared rays.
6. A method of producing pulverized abrasive materials for sand blasting, comprising the steps of:
carrying out a first phase by adding two parts of a thermo-setting resin to which one part of a setting catalyst has been added, to 100 parts of a pulverized material of grade No. 4, selected from the group consisting of silica sand and slag; uniformly mixing particles of said resin with said resin and catalyst while blowing heated air thereinto at about 80 to 100°C, constituting a first heat treatment, so as to coat the resulting pulverized sand-blasting abrasive material with the resin in a fixed thickness, to dry and to thermally set the resin coating on the particles of abrasive material without causing coalescence of the particles; and carrying out a second, separate phase by a subsequent re-heating treatment of said coated particles at a temperature of about 300°C while effecting stirring of said particles by means of a heated gas stream or by means of a vibration producing device, so as to change chemically the resin coating obtained on the abrasive material in the first heat treatment, and to render the coating in-soluble and infusible while at the same time leaving the coated abrasive material in a pulverized condition.
carrying out a first phase by adding two parts of a thermo-setting resin to which one part of a setting catalyst has been added, to 100 parts of a pulverized material of grade No. 4, selected from the group consisting of silica sand and slag; uniformly mixing particles of said resin with said resin and catalyst while blowing heated air thereinto at about 80 to 100°C, constituting a first heat treatment, so as to coat the resulting pulverized sand-blasting abrasive material with the resin in a fixed thickness, to dry and to thermally set the resin coating on the particles of abrasive material without causing coalescence of the particles; and carrying out a second, separate phase by a subsequent re-heating treatment of said coated particles at a temperature of about 300°C while effecting stirring of said particles by means of a heated gas stream or by means of a vibration producing device, so as to change chemically the resin coating obtained on the abrasive material in the first heat treatment, and to render the coating in-soluble and infusible while at the same time leaving the coated abrasive material in a pulverized condition.
7. A coated abrasive material, wherein the material is selected from silica sand or slag, and the coating which directly overlies said material is a thermosetting resin selected from a phenolic resin, a urea resin, a melamine resin, a polyester resin or an alkyd resin, each including a setting catalyst, which coating is substantially insoluble and infusible on effect of re-applied heat, said coated abrasive material being in the form of fine, free flowing discrete particles, and said abrasive material being further characterized by having a higher degree of uniformity with respect to particle size, than conventional abrasive materials, and in that a greater proportion of the abrasive particles are re-usable than is the case with conventional abrasive materials; said coating increasing the strength of the abrasive material by penetrating into cracks inherent in the abrasive material so that a substantial proportion of the pulverized abrasive material can be recovered after the sand blasting for re-use; whereby the heat, generated by impact when the abrasive material is blown against a surface to be cleaned by the sand blasting, leaves the insoluble and infusible coating in this state, and actually continues the setting of that coating so that sand-blasting efficiency is increased; and whereby dust formation during the sand blasting is reduced, thereby increasing environmental protection.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA285,000A CA1094332A (en) | 1977-08-18 | 1977-08-18 | Sand blasting abrasive materials and method of producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA285,000A CA1094332A (en) | 1977-08-18 | 1977-08-18 | Sand blasting abrasive materials and method of producing the same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094332A true CA1094332A (en) | 1981-01-27 |
Family
ID=4109354
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA285,000A Expired CA1094332A (en) | 1977-08-18 | 1977-08-18 | Sand blasting abrasive materials and method of producing the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1094332A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5066335A (en) * | 1989-05-02 | 1991-11-19 | Ogilvie Mills Ltd. | Glass-like polysaccharide abrasive grit |
| US6159257A (en) * | 1998-10-21 | 2000-12-12 | Adm Agri-Industries, Ltd. | Water-resistant, glass-like, polysaccharide abrasive grits and method of making same |
| CN115207163A (en) * | 2022-07-25 | 2022-10-18 | 正泰新能科技有限公司 | Silicon wafer texturing method, solar cell and manufacturing method of solar cell |
-
1977
- 1977-08-18 CA CA285,000A patent/CA1094332A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5066335A (en) * | 1989-05-02 | 1991-11-19 | Ogilvie Mills Ltd. | Glass-like polysaccharide abrasive grit |
| US6159257A (en) * | 1998-10-21 | 2000-12-12 | Adm Agri-Industries, Ltd. | Water-resistant, glass-like, polysaccharide abrasive grits and method of making same |
| CN115207163A (en) * | 2022-07-25 | 2022-10-18 | 正泰新能科技有限公司 | Silicon wafer texturing method, solar cell and manufacturing method of solar cell |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4333743A (en) | Sand-blasting abrasive materials and method of producing the same | |
| JP3626098B2 (en) | Beads for grinding, bead manufacturing method and manufacturing apparatus | |
| US11975332B2 (en) | Impact reactor | |
| CA1094332A (en) | Sand blasting abrasive materials and method of producing the same | |
| JPH02504626A (en) | Method and device for preparing slag from waste combustion furnace | |
| JP4744210B2 (en) | Method for producing recycled asphalt mixture | |
| EP1414601B1 (en) | Method of preparing foundry sand | |
| US4002462A (en) | Ore beneficiation method and apparatus | |
| KR100402412B1 (en) | Regenerating apparatus of molding sand, and regenerating method thereof | |
| US20200215506A1 (en) | Recycled asphalt production apparatus | |
| AU573606B2 (en) | Treating used foundry sand and the like | |
| GB1571239A (en) | Abrasive materials and a method of producing such materials | |
| JP2021102216A (en) | Mold reconditioned sand, resin coated sand and mold | |
| GB2458975A (en) | Handling aggregate in an asphalt plant | |
| GB2485229A (en) | Apparatus for drying particulate materials | |
| JP3732429B2 (en) | Pretreatment equipment and pretreatment method for ash melting furnace | |
| JPS61501378A (en) | Sand recycling equipment including heat regenerator/sand-to-sand heat exchanger combination equipment | |
| JP2002212430A (en) | Method for preparing recycled hot asphalt mixture containing waste glass grains | |
| JP3373098B2 (en) | Vibration granulator and method | |
| EP0105884A1 (en) | Thermal sand reclamation system | |
| US4565328A (en) | Sand reclamation system with thermal pipe reclaimer apparatus | |
| JP5683926B2 (en) | Concrete and method for producing concrete | |
| JP2021102215A (en) | Mold reconditioned sand, resin coated sand and mold | |
| CN104550693B (en) | Pit-free regeneration treatment device for resin sand | |
| JPH07314080A (en) | Method for reconditioning molding sand |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |