EXPANDABLE COPOLYMER RESIN USED FOR MANUFACTURING LOST FOAM CASTING MODEL AND PREPARATION METHOD THEREOF

Abstract

The invention discloses an expandable copolymer resin used for manufacturing a lost foam casting model and a preparation method thereof, wherein the molecular weight of the expandable copolymer resin is 150000-300000, and the expandable copolymer resin comprises mixed monomers, deionized water, a cellulose ether dispersant, sodium salt, an initiator, a foaming agent and a molecular weight regulator; the mixed monomers comprise MMA and ST, wherein MMA accounts for 70-95% wt of the mixed monomers, and ST accounts for 5-30% wt of the mixed monomers. The model formed by the expandable copolymer resin has the advantage of reducing or eliminating carbon defects of castings when casting cast iron and cast steel.

Claims

1. An expandable copolymer resin used for manufacturing a lost foam casting model, comprising the following components in parts by weight: 100 parts of mixed monomers; 150-250 parts of deionized water; 0.3-0.6 parts of cellulose ether dispersant; 0.15-0.45 parts of sodium salt; 0.25-0.50 parts of initiator; 8-15 parts of foaming agent; 0.1-0.5 parts of molecular weight regulator; the mixed monomers comprise methyl methacrylate and styrene, the methyl methacrylate accounts for 70-95 wt % of the mixed monomers, and the styrene accounts for 5-30 wt % of the mixed monomers; the sodium salt comprises at least one of sodium sulfate, sodium pyrophosphate and sodium dichromate; the initiator comprises at least two of tert-butyl peroxyisooctanoate, benzoyl peroxide and tert-butyl peroxybenzoate; the foaming agent is consisted of n-pentane, isopentane and petroleum ether in a mass part ratio of 8:(2-6):4; the molecular weight regulator comprises at least one of divinylbenzene, ethylene glycol dimethacrylate, C8-C12 alkyl mercaptan, carbon tetrabromide and methyl styrene dimer; the molecular weight of the expandable copolymer resin is 150,000 to 300,000.

2. The expandable copolymer resin used for manufacturing a lost foam casting model according to claim 1, wherein the mixed monomers further comprise an auxiliary agent, and wherein the auxiliary agent accounts for 0-5wt % of the mixed monomers, the MMA accounts for 65-95% wt of the mixed monomers, and the ST accounts for 5-30% wt of the mixed monomers; the auxiliary agent comprises at least one of butyl acrylate and butyl methacrylate.

3. The expandable copolymer resin used for manufacturing a lost foam casting model according to claim 2, wherein the auxiliary agent is consisted of butyl acrylate and butyl methacrylate in a ratio of 1:1 in parts by mass.

4. The expandable copolymer resin used for manufacturing a lost foam casting model according to claim 1, wherein the expandable copolymer resin further comprises 1-1.5 parts by weight of plasticizer, wherein the plasticizer comprises at least one of fumaric acid and polycaprolactone.

5. The expandable copolymer resin used for manufacturing a lost foam casting model according to claim 1, wherein the expandable copolymer resin further comprises 0.5-1.5 parts by weight of activating agent, wherein the activating agent comprises at least one of zinc oxide, stearate, carbonate and phosphate.

6. The expandable copolymer resin used for manufacturing a lost foam casting model according to claim 1, wherein the expandable copolymer resin further comprises 0.1-0.4 parts by weight of additive, wherein the additive comprises at least two of polyurethane, polyether and polycaprolactone.

7. The expandable copolymer resin used for manufacturing a lost foam casting model according to claim 1, wherein the expandable copolymer resin further comprises 0.05-0.15 parts by weight of stabilizer, wherein the stabilizer is consisted of an antimony mercaptide stabilizer and calcium stearate.

8. A preparation method of the expandable copolymer resin used for manufacturing the lost foam casting model according to claim 1, comprising the steps of: step 1, fully mixing the deionized water, the cellulose ether dispersant and the sodium salt according to parts by weight to form a first mixture; step 2, fully mixing the mixed monomers, the foaming agent, the initiator, the molecular weight regulator, the plasticizer, the activating agent, the additive and the stabilizer according to parts by weight to obtain a second mixture; step 3, adding the second mixture obtained in step 2 into the first mixture obtained in step 1, mixing for 15-20 min, heating to 65-95 C., reacting for 7-16 h under the pressure of 3-6 kg to obtain a first product; step 4, sequentially cooling, washing, dehydrating and drying the first product obtained in step 3 to obtain a second product; and step 5, screening the second product obtained in step 4 to obtain granular expandable copolymer resin with the particle size of 20-60 meshes; in step 4, the cooling is carried out to a temperature of 35-45 C., and the drying temperature is 50-60 C.

9. The preparation method of the expandable copolymer resin used for manufacturing the lost foam casting model according to claim 8, wherein the plasticizer is added and mixed together to obtained the second mixture at step 2.

10. The preparation method of the expandable copolymer resin used for manufacturing the lost foam casting model according to claim 8, wherein the activating agent is added and mixed together to obtained the second mixture at step 2.

11. The preparation method of the expandable copolymer resin used for manufacturing the lost foam casting model according to claim 8, wherein the additive is added and mixed together to obtained the second mixture at step 2.

12. The preparation method of the expandable copolymer resin used for manufacturing the lost foam casting model according to claim 8, wherein the stabilizer is added and mixed together to obtained the second mixture at step 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0063] Hereinafter, the present invention will be described in detail with reference to Examples.

[0064] Example 1: an expandable copolymer resin used for manufacturing a lost foam casting model comprises components and their corresponding masses as shown in Table 1 and was prepared through the steps of:

[0065] step 1, fully mixing deionized water, a cellulose ether dispersant and sodium salt to form a first mixture;

[0066] step 2, fully mixing mixed monomers, a foaming agent, an initiator and a molecular weight regulator to obtain a second mixture;

[0067] step 3, adding the second mixture obtained in step 2 into the first mixture obtained in step 1, mixing for 15-20 min, heating to 80 C., reacting for 7 h, then heating to 95 C., reacting for 2 h under the pressure of 3-6 kg to obtain a first product;

[0068] step 4, cooling the first product obtained in step 3 to a temperature of 35-45 C., washing with water, dehydrating, and fully drying at a temperature of 50-60 C. to obtain a second product; and

[0069] step 5, screening the second product obtained in step 4 to obtain granular expandable copolymer resin with a particle size of 20-60 meshes.

[0070] A method for preparing a casting, comprising the steps of:

[0071] selecting the granular expandable copolymer resin obtained in step 5 according to casting requirements, prefoaming, carrying out compression modeling on a modeling press, drying the modeled model, coating, drying, putting into a sand box for casting, and casting to obtain a casting.

[0072] In particular, the cellulose ether dispersant was consisted of hydroxyethyl cellulose ether and hydroxypropyl cellulose ether in a ratio of 1:1 by mass; the sodium salt was consisted of sodium sulfate, sodium pyrophosphate and sodium dichromate in a ratio of 1:1:1 by mass; the foaming agent was consisted of n-pentane, isopentane and petroleum ether in a ratio of 8:(2-6):4 by mass; the initiator was consisted of tert-butyl peroxyisooctanoate and tert-butyl peroxybenzoate in a ratio of 1:1 by mass; and the molecular weight regulator was consisted of carbon tetrabromide and methyl styrene dimer in a ratio of 1:1 by mass.

[0073] Example 2: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 1 in components included therein and their corresponding masses, as shown in Table 1.

[0074] Example 3: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 1 in the components included therein and their corresponding masses, as shown in Table 1, and, in step 3, heating to 70 C. and reacting for 10 h.

[0075] Example 4: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 1 in the components included therein and the corresponding masses thereof, as shown in Table 1, and in step 3, heating to 75 C., reacting for 8 h, and then heating to 93 C. and reacting for 4 h.

[0076] Examples 5-8: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 1 in the components included therein and their corresponding masses, as shown in Table 1.

[0077] Example 9: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 1 in that 1 kg fumaric acid was also added in step 2.

TABLE-US-00001 TABLE 1 Components included in Examples 1-8 and their corresponding masses (kg) Mass Example Example Example Example Example Example Example Example Components 1 2 3 4 5 6 7 8 Mixed monomer MMA 70 70 70 70 65 95 80 72 ST 30 25 30 25 30 5 15 24 Butyl acrylate 0 0 0 5 2.5 0 2.5 2 Butyl methacrylate 0 5 0 0 2.5 0 2.5 2 Deionized water 250 200 250 250 250 150 200 180 Cellulose ether dispersant 0.35 0.3 0.35 0.35 0.35 0.3 0.6 0.5 Sodium Salt 0.3 0.3 0.3 0.3 0.3 0.15 0.45 0.25 Initiator 0.4 0.4 0.4 0.4 0.4 0.25 0.5 0.35 Foaming agent 8 10 15 10 10 12 8 15 Molecular weight regulator 0.5 0.3 0.15 0.3 0.4 0.1 0.25 0.15

[0078] Example 10: an expandable copolymer resin used for manufacturing a lost foam casting model, which differs from Example 9 in that 1.2 kg fumaric acid was added in step 2.

[0079] Example 11: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 9 in that 1.5 kg fumaric acid was added in step 2.

[0080] Example 12: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 1 in that 1.1 kg polycaprolactone was also added in step 2.

[0081] Example 13: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 12 in that 1.3 kg plasticizer was added in step 2, which was consisted of fumaric acid and polycaprolactone in a ratio of 1:2 by weight.

[0082] Example 14: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 12 in that 1.5 kg plasticizer was added in step 2, which was consisted of fumaric acid and polycaprolactone in a ratio of 1:1 by weight.

[0083] Example 15: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 9 in that 0.5 kg zinc oxide and 0.5 kg stearate were also added in step 2.

[0084] Example 16: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 15 in that 0.1 kg polyurethane and 0.3 kg polyether were also added in step 2.

[0085] Example 17: an expandable copolymer resin used for manufacturing a lost foam casting model, which differed from Example 16 in that 0.05 kg antimony mercaptide stabilizer and 0.1 kg calcium stearate were also added in step 2.

[0086] Comparative Example 1: a lost foam production process of an automobile engine cylinder body, which differed from Example 1 in that the process comprised the steps of:

[0087] step 1, the bead pre-expanding process: firstly, performing a pre-foaming process of selected EPS beads for 40-60 s under the conditions of pipeline pressure of 0.1 Mpa-0.2 Mpa, expansion chamber pressure of 0.03 Mpa-0.06 Mpa and temperature of 90 C.-100 C. ; and then carrying out a curing treatment for (2-12)h at a temperature of (20-25) C. such that the EPS bead density was maintained at 2.1-2.2 g/L.

[0088] step 2, the blank model fabricating process: firstly, subjecting the blank model of the automobile engine cylinder body to fragment processing according to the structural characteristics of the engine to be manufactured, specifically adopting a method of external integral model manufacturing and internal inlaying of a cylinder sleeve; and then filling the EPS beads cured after pre-expanding in step 1 into a blank model for modeling by adopting a material suction filling method;

[0089] step 3, the drying process: drying the blank model manufactured in step 2 for (10-12)h under the conditions that the temperature is (45-50) C. and the humidity is (15-20)RH.

[0090] step 4, the model bonding process: bonding the parts dried in step 2 together by using a model bonding adhesive, and meanwhile, pre-coating a paste coating locally.

[0091] step 5, a dip coating process: dip coating a coating on the lost foam pattern bonded in step 4, including three steps of first dip coating, recoating and selective coating; wherein in the first dip coating, integrally dip coating the blank model bonded in step 4, and drying according to step 6; in recoating, carrying out a secondary dip coating on the dried blank model integrally, and drying according to step 6; and finally in selective coating, locally pouring and coating the dried blank model, filling resin sand and drying according to step 6.

[0092] step 6, the drying process after dip coating: performing drying treatment for (36-48)h on the blank model that was dip-coated in step 5 under the conditions that the temperature is (50-60) C. and the humidity is (15-20);

[0093] step 7, the modeling casting process: placing a sand box under a shower sand filling machine to fill sand while starting a vibrating table; placing the blank model dried in step 6 on modeling sand, and manually filling 70/100 meshes of modeling sand locally by using a pressurizing sand flushing machine; starting the sand filling machine to fill sand, and stopping sand filling and compacting when the modeling sand reaches a vertical pouring head of the blank model; cleaning the modeling sand of the vertical pouring head at the upper end of the blank model sprue, smearing bonding adhesive, adhering a filter screen, placing a sprue cup, and covering plastic cloth on a sand box; starting the sand filling machine to fill the sand box until it was full; connecting a negative pressure pipe, starting a negative pressure machine, pouring molten metal into the blank model from the sprue cup, keeping casting under the conditions that the casting negative pressure is 0.04 Mpa-0.06 Mpa, the casting speed is 5 kg/s and the casting temperature is 1490 C.-1500 C. , and finally obtaining a cast engine cylinder body; through this production process, sand sticking and water leakage can be effectively prevented; the qualified rate of the produced automobile engine cylinder body is improved and can reach 94%-97%, rendering a better quality of the engine cylinder body.

[0094] Comparative Example 2: a preparation method of modified expandable polystyrene copolymer particles special for a lost foam, which differed from the Example 1 in that the preparation method comprised the steps of:

[0095] taking 120 parts of water, 95 parts of styrene, 5 parts of methyl methacrylate, 1 part of suspending agents and 0.01 part of anionic surfactants; 0.2 parts of benzoyl peroxide; 0.1 parts of nucleating agents; 0.3 parts of organic bromine; 0.2 parts of dicumyl peroxide; 0.1 parts of t-butyl peroxybenzoate; 0.05 parts of molecular weight regulators; and then sequentially adding water, the suspending agents, the surfactants, styrene, methyl methacrylate, benzoyl peroxide, the nucleating agents, organic bromine, dicumyl peroxide and tert-butyl peroxybenzoate into a reactor, sealing and uniformly mixing.

[0096] The reactor was then heated at a rate of 0.5 C./min and held at constant temperature for 400 minutes as the temperature was raised to 83 C.

[0097] After capping, nitrogen replacement was carried out for 3 times and 6 parts of foaming agents were pressed in.

[0098] The reactor was then heated at a rate of 0.5 C./minute to a reaction temperature of 120 C. and a pressure of 0.65 mPa and held at this temperature and pressure for 300 minutes.

[0099] And then the reactor as cooled by using cooling water, so that the temperature of the materials in the reactor is reduced to 35 C.

[0100] And then dehydrating, drying and screening of the materials were carried out.

[0101] And then, 0.3 parts of surface coating agents were added, stirring was conducted, the materials and the surface coating agents were fully and uniformly mixed, and packaged after mixing to obtain the modified expandable polystyrene copolymer particles special for the lost foam.

[0102] Casting Quality Test

[0103] Test samples: a model made using the expandable copolymer resin used for manufacturing a lost foam casting model obtained in Examples 1-17 is adopted, the castings obtained were taken as test samples 1-17, and a model made using the expandable copolymer resin used for manufacturing a lost foam casting model obtained in Comparative Examples 1-2 is adopted, the castings obtained were taken as comparative samples 1-2. Each of the test samples and comparative samples includes 100 ductile iron pipe pieces (d=200 mm), 100 four-cylinder bodies (gray iron workpiece) and 100 ductile iron cylinder barrel bodies (d=300*700 complete workpiece).

[0104] Test method: the surface condition of ductile iron pipe (d=200 mm), four-cylinder bodies (gray iron workpiece) and ductile iron cylinder barrel bodies (d=300*700 complete workpiece) in each of the test samples and comparative samples was observed, the density of the model and the qualified rate were examined, recorded and analyzed.

[0105] Test results: the density, surface condition and qualified rate of ductile iron pipe pieces, four-cylinder bodies and ductile iron cylinder bodies in test samples 1-17 and comparative samples 1-2 are shown in Table 2.

TABLE-US-00002 TABLE 2 Density, surface condition, qualified rate of ductile iron pipe pieces, four-cylinder bodies, and ductile iron cylinder barrel bodies in test samples 1-17 and comparative samples 1-2 Test index Ductile iron pipe piece Four-cylinder body Ductile iron cylinder barrel body Model (d = 200 mm) (gray iron workpiece) (d = 300*700 complete workpiece) density Model surface Qualified Qualified Qualified Test samples (g/L) condition Surface condition rate (%) Surface condition rate (%) Surface condition rate (%) Test sample 1 21 smooth surface Good surface quality 92 Good surface quality 96 Good surface 94 quality Test sample 2 22 smooth surface Good surface quality 93 Good surface quality 93 Good surface 96 quality Test sample 3 22 smooth surface Good surface quality 91 Good surface quality 91 Good surface 96 quality Test sample 4 21 smooth surface Good surface quality 92 Good surface quality 94 Good surface 93 quality Test sample 5 21 smooth surface Good surface quality 98 Good surface quality 95 Good surface 96 quality Test sample 6 22 smooth surface Good surface quality 91 Good surface quality 90 Good surface 93 quality Test sample 7 21 smooth surface Good surface quality 91 Good surface quality 92 Good surface 93 quality Test sample 8 21 smooth surface Good surface quality 92 Good surface quality 91 Good surface 95 quality Test sample 9 22 smooth surface Good surface quality 94 Good surface quality 92 Good surface 95 quality Test sample 10 22 smooth surface Good surface quality 93 Good surface quality 91 Good surface 95 quality Test sample 11 22 smooth surface Good surface quality 94 Good surface quality 92 Good surface 95 quality Test sample 12 21 smooth surface Good surface quality 95 Good surface quality 92 Good surface 95 quality Test sample 13 22 smooth surface Good surface quality 95 Good surface quality 93 Good surface 95 quality Test sample 14 21 smooth surface Good surface quality 95 Good surface quality 93 Good surface 95 quality Test sample 15 21 smooth surface Good surface quality 95 Good surface quality 94 Good surface 95 quality Test sample 16 21 smooth surface Good surface quality 95 Good surface quality 93 Good surface 95 quality Test sample 17 21 smooth surface Good surface quality 95 Good surface quality 93 Good surface 95 quality comparative 25 Relatively rough Relatively poor 20 Relatively poor 35 Relatively poor 6 sample 1 surface surface quality surface quality surface quality comparative 24 Relatively smooth Relatively good 78 Relatively good 83 Relatively good 88 sample 2 surface surface quality surface quality surface quality

[0106] As can be seen from Table 2, the ductile iron pipe pieces (d=200 mm), the four-cylinder bodies (gray iron workpiece) and the ductile iron cylinder barrel bodies (d=300*700 complete workpiece) in the test samples 1-17 are smooth in their surfaces and good in quality, and the qualified rate of the ductile iron pipe pieces (d=200 mm) is up to 91%, and up to 96% in the best cases; the qualified rate of the four-cylinder bodies (gray iron workpiece) is up to 90%, and up to 96% in the best cases; the qualified rate of the ductile iron cylinder barrel bodies (d=300*700) is up to 93%, and up to 97% in the best cases.

[0107] However, in comparative sample 1, the ductile iron pipe pieces (d=200 mm), four-cylinder bodies (gray iron workpiece) and ductile iron cylinder barrel bodies (d=300*700 complete workpiece) were rough in their surfaces and the quality was poor, and the qualified rate of ductile iron pipe pieces (d=200 mm) was only 20%; the qualified rate of the four-cylinder bodies (gray iron workpiece) was only 35%; the qualified rate of the ductile iron cylinder barrel bodies (d=300*700) was only 6%. The above significant differences were due to that the mixed monomers used and the mixed monomers in the test samples 1-17 were different in their components and the proportion thereof, which showed that it was difficult to meet the requirement of high-quality castings taking the EPS as a raw material of the lost foam.

[0108] In comparative sample 2, the surface quality of ductile iron pipe pieces (d=200 mm), four-cylinder bodies (gray iron workpiece) and ductile iron cylinder barrel bodies (d=300*700 complete workpiece) was better, and the qualified rate of ductile iron pipe pieces (d=200 mm) was 78%; the qualified rate of the four-cylinder bodies (gray iron workpieces) can reach 83%; the qualified rate of ductile iron cylinder barrel bodies (d=300*700 complete workpieces) can reach 88%, which, in comparison with comparative sample 1, showed some breakthrough, indicating that the use of MMA and ST to prepare a lost foam can improve the surface condition and qualified rate of castings to some extent. However, when comparing comparative sample 2 with test samples 1-17, although both test samples 1-17 and comparative sample 2 used MMA and ST reaction for preparing the lost foam, comparative sample 2 was inferior regarding the casting surface condition, surface quality or qualified rate, indicating that the components of the mixed monomers and the corresponding proportion did have a certain impact on the casting surface condition, surface quality and qualified rate. In addition, although the difference between the qualified rates of different castings in test samples 1-17 and comparative sample 2 was not very great, an improvement of the qualified rate is of great significance to a relatively mature industry.

[0109] The above-mentioned examples are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions falling within the spirit of the present invention fall within the scope of the present invention. It should be noted that those skilled in the art will appreciate that various modifications and adaptations can be made without departing from the spirit and scope of the present invention.