- Email: [email protected]
Recycling of waste PVC leather and PVC urethane in the automobile industry
Consemotion & Recycling, Printed in Great Britain.
Vol.
10, No. 4, pp. X5-272,
0361-
1987.
3658/87 %3.00+ .OO Pergamon Press plc
RECYCLING OF WASTE PVC LEATHER AND PVC URETHANE IN THE AUTOMOBILE INDUSTRY SEIJI MIYAMA Oppama Plant, Nissan Motor Co. Ltd, I Natsushima-cho, Yokosuka 237, Japan
Abstract - Waste plastics are low in scrap value in the automobile industry and are most difficult to dispose of for reutilization. The waste plastics have been disposed of by incineration and reclamation as measures for preventing industrial pollution, but these measures involved various problems and quite a different idea could be successfully developed to effectively reutilize them. The case of reutilization is introduced here.
1. INTRODUCTION The waste PVC leather and PVC urethane discharged from the Seat Fabrication Shop in our plant amounts to about 450 tons per year, and its disposal had been a serious problem. Burning generates black smoke, and also corrosive gases, such as hydrogen chloride, which are detrimental to furnace walls. Disposal for land reclamation involves many problems, such as lack of biodegradability and of resulting weak ground, owing to poor consolidation. The case introduced here started from the necessity of taking measures against pollution, and is still practised now for recycling of wastes in automobile parts.
2. DECISION TO REUTILIZE
THE WASTE
The waste is generally discharged as a mixture and cannot be reused in its existing state. Reutilization of waste as a resource must start from its separation into constituent materials. It is not too much to say that a successful separation reaches halfway to successful reutilization as a resource. Examination of how wastes similar to ours (Fig. 1) are recycled in other industries showed that thick waste PVC leather discharged after the production of shoes and bags is separated into PVC grains and cloth by crushing and air classification, to reuse the PVC grains as a raw material for the product. By contrast, waste PVC leather and PVC urethane discharged from our plant comprises fragments generated in the production of car seats and interior products, and includes a large amount of thin cloth coated with thin PVC, most of which has urethane foam sewn together as a cushion. How to separate the mixture wastes efficiently into their constituent materials was a large problem, and examination started from this aspect. Concurrently, possible applications of recovered PVC and urethane were also examined, as described below. In general, the principal difficulty in the reutilization of wastes is the difficulty of maintaining continuity. One of the reasons concerns profitability, but a more serious fact is that demand continually changes, depending on the situation for the users of processed wastes. Processed waste suppliers wish demand to continue, but this is difficult to achieve. Therefore, our plant decided to use the wastes for our automobile parts with the greatest importance attached to continuity. 265
SEIJI MIYAMA
266
Glued (Waste PVC leather)
Soft urethane
(b)
foam
Cloth
Glued (Waste urethane)
I
Sewn (Waste PVC urethane)
Fig. 1. Kinds of wastes from seat production.
Examination reutilization
for
\
)
Examination on the method for separating constituent materials
Present flow
1
Fig. 2. Recycling flow. Materials to be crushed
Fig. 3. Crushing test equipment.
Successful research and development for the preparation of automobile parts from the waste took place under the cooperation of a parts maker. In addition, an efficient air separation and recovery device was developed, and regular operation began from 1975. The recycling system has been used from that date, although the applied parts, and the share of processing, have changed. Figure 2 shows the recycling flow.
RECYCLING OF WASTE PVC
261
Table 1. Experimental results of crushing Crushed quantity (kg) 17.0
Period of time (min) 8.0
Waste PVC urethane Waste PVC leather
13.2
Waste PVC urethane
No.
Sample Waste PVC leather
Crushing capability (kg hr-‘) 127
Crusher current (A) 20-30
Urethane pieces are too large.
13.5
58.6
20-30
Separation from PVC is poor.
19.0
10.0
114
30-50
If urethane can be blown away when held in the hand, then PVC can be easily separated.
7.0
8.0
52.5
30-50
Cloth adheres to PVC.
Crushed state
1
2
Waste PVC teather
/
and PVC urethane
-7
Feed convevor
YI
I 0
Cocyse ausher
I
Fan
thane chips
equipment
has
registered
in Japan.1
Fig. 4. Materials separation and recovery equipment flow.
3. EXAMINATION
OF THE METHOD FOR SEPARATING
MATERIALS
The wastes discharged from the shop include three types, as shown in Fig. 1. Of these, sewn three-layer articles (c) are generated in the largest quantities. Waste is no more than that, if it is not processed for separation into constituent materials. As for the methods for separating the constituent materials, for type (a), erosion of cloth by sulfuric acid is well known, but has not been used practically for (b) and (c) as far as we know. It was therefore necessary to develop a new separation method.
SEIJI MIYAMA
268
Waste PVC leather Waste urethane
Matertat
selecting
Waste cloth
f i ncinerated)
Fig. 5. Breakdown of recovered materials.
Table 2. Separation standard
Urethane
Specific gravity
Form
Recovered material
To be crushed into lo- 30 mm square pieces.
Purchased raw material (urethane 100%) - 0.02
To contain less than about 30 wt % of PVC and cloth.
Recovered material - 0.065
Chips
To be grains of 1 - 3 mm (the cloth adhering to the back of PVC may remain attached)
PVC Grains
Not to contain urethane.
Molded head rest
Moided arm rest FiUer for trunk mat
Fig. 6. Regions of applied parts (example).
It was concluded th# the most orthodox method, i.e. of ‘crushing and air separation* would be the optimum, on the precondition that the recovered constituent materials are not changed in the material.
269
RECYCLING OF WASTE PVC (a)
Molding of head rest and arm rest
Urethane
chips..
Worsted.. Binder..
(b) Production
.,
85% 10% 2
-
Mixing
Mold fiiling
-
_
_
Hot press
Product (I
of trunk mat
Table 3. Processed tonnage and recovered tonnage Kind of waste
output
Input
Kind of
465
Urethane chins
36%
t yr-’
PVC grains
72t
material Waste PVC leather
437tyr-’ Waste urethane
28 tyr-’ Waste PVC urethane
Waste cloth (incinerated)
Table 4. Annual processing cost
Depreciation Tax, interest and insurance
73.4 million yen 16.9 million yen 0.7 milhon yen
Sub-total Repair expenses Electric power charge Labor cost
17.6 million 3 .O million 3.4 million 10.8 million
Sub-total Total
17.2 million yen 34.8 million ven
Equipment investment Standing expenses cost Variable expenses
Unit cost of processing = ~~~~~~~~i$n~t
= 34’8 y$i,,
yen yen yen yen
yen * 80 yen kg-’
Separation tests
Based on the above conclusion, it was decided to make preliminary tests for obtaining data for determining the specifications of machines. (i) Samples. PVC film + cloth, glued (waste PVC leather). (PVC film + cloth) + (urethane + cloth), sewn (waste PVC urethane).
270
SEIJI MIYAMA Table 5. Amount of annual cost reduction, by material
cost Material used
Product cost When newly bought material is used
Annual consumption (2)
Annual cost reduction (1) x (2)
108 yen kg-’
365 000 kg
39.4 million yen
513 yen kg-’
Urethane When regenerated material is used When newly bought material is used
reduction per weight (I)
405 187 yen kg-’ 105 yen kg-’
PVC When regenerated material is used
72 OOOkg
7.6 million yen
82 Total
47.0 million yen
Overall effect Total annual cost reduction (Table 5) - Total annual processing cost (Table 4) = Effect. 47.0 million yen - 34.8 million yen = 12.2 million yen y-‘.
(ii) Crushing test equipment. Figure 3 shows the outline of the equipment. Crusher: rotary shear type, blade width 450 mm, with two fixed blades and five rotating blades, consumption 15 kW. Exhaust fan: turbo type, 23 m3 min-‘, 95 mm Aq, 0.75 kW. Recovery cyclone: barrel 600 diameter. (iii) Experimental results. As shown in Table 1, the recovery of urethane alone could be achieved by crushing only. However, the recovery of PVC required separation from the cloth, and it was found that actual operation required the additional use of a fine crusher.
4. OUTLINE OF THE MATERIALS
SEPARATION
AND RECOVERY EQUIPMENT
The following equipment was developed on the basis of the results of the above separation tests, considering workability, costs. Figure 4 shows the flowsheet. Process (i) Waste PVC leather and PVC urethane are put into a coarse crusher. Each piece should be about 300 mm square; larger pieces should be cut beforehand. (ii) The coarse crusher comminutes to 10 - 30 mm square pieces, and allows them to fall onto a vibrating conveyor. (iii) Air is sent from the underside of the vibrating conveyor, to agitate the crushed pieces. (iv) Light urethane chips are recovered by suction nozzles. (v) Heavy PVC is further crushed into 1 to 3 mm grains by fine crushers and recovered by a classifier. Breakdown of recovered materials The balance of the recovered materials is as in Fig. 5.
271
RECYCLING OF WASTE PVC
States of recovered materials If the waste PVC leather and PVC urethane were separated more accurately into the respective constituent materials, they would find wider application, but on the other hand, at a higher cost. Compromise is inevitable in this respect. Our plant uses the separation standards shown in Table 2. SELECTION
OF APPLICABLE
AUTOMOBILE
PARTS
The use of the processed waste for automobile parts is limited in application, and parts using the processed wastes should be the less-visible and less-functionally important. From this point of view, parts were examined by the value analysis technique, and the most suitable ones selected. Applied parts: Urethane chips: molded head rest and arm rest; PVC grains: filler for trunk mat. Figure 6 shows the regions of the applied parts. These parts were then molded, using the purchased raw materials only. As a matter of course, careful tests had been repeated by trial production for the parts, before regular production. The tests included: (i) Sensory tests for resiliency, cushioning, etc. (ii) Interlayer peeling tests between different materials. (iii) Durability tests. These tests were repeated to decide the optimum mixing ratios. 6. PRODUCTION
OF AUTOMOBILE
PARTS
The head rest, arm rest and trunk mat are produced according to the flow shown in Fig. 7. 7. QUALITY OF REGENERATED
MATERIALS
Provided that automobile parts display their proper commercial functions, it is of no importance whether they are made of purchased materials or regenerated materials. In our case, there was the rather unexpected result that the regenerated materials were better. For example, when a conventional product of urethane (100% purchased) needs a certain hardness, aggregate has to be added as required. However, the mixing of the regenerated material provides the proper hardness, eliminating the need for adding aggregate. As a considerable side effect, the cushioning property can be freely changed by changing the mixing ratio. 8. COSTS The actual statistics in our plant were as given below. (i) Processed tonnage and recovered tonnage are listed in Table 3. (ii) Annual processing costs are listed in Table 4. (iii) Annual cost reduction, by material, are listed in Table 5. The overall effect is (Total annual cost reduction) - (Total annual processing cost). Our plant achieves an annual positive effect of about 12.2 million yen. Including the expenses for land reclamation executed in the past, the effect corresponds to about 40 million yen.
212
SEIJI MIYAMA
9. CONCLUSIONS As described above, the reutilization of wastes in the plant began from the necessity of taking measures to prevent pollution; however, waste is now indispensably required as a raw material. The system is not, however, problem-free. In the past decade, the seats have been enhanced in quality, a drastic reduction in the use of PVC, and the use of woven fabric which is difficult to recycle, is increasing. In addition, the cost of solid moldings, using no regenerated material, has declined, causing severe competition with the regenerated materials. The reutilization of wastes as resources is not always simple. The recycling of wastes as a resource is always confronted by such difficulties. This case has the advantage that the regenerated materials are used for mass-produced motor vehicles, which provide a continuous demand. At our plant, we intend both to continue this project and to develop new applications.
Vol.
10, No. 4, pp. X5-272,
0361-
1987.
3658/87 %3.00+ .OO Pergamon Press plc
RECYCLING OF WASTE PVC LEATHER AND PVC URETHANE IN THE AUTOMOBILE INDUSTRY SEIJI MIYAMA Oppama Plant, Nissan Motor Co. Ltd, I Natsushima-cho, Yokosuka 237, Japan
Abstract - Waste plastics are low in scrap value in the automobile industry and are most difficult to dispose of for reutilization. The waste plastics have been disposed of by incineration and reclamation as measures for preventing industrial pollution, but these measures involved various problems and quite a different idea could be successfully developed to effectively reutilize them. The case of reutilization is introduced here.
1. INTRODUCTION The waste PVC leather and PVC urethane discharged from the Seat Fabrication Shop in our plant amounts to about 450 tons per year, and its disposal had been a serious problem. Burning generates black smoke, and also corrosive gases, such as hydrogen chloride, which are detrimental to furnace walls. Disposal for land reclamation involves many problems, such as lack of biodegradability and of resulting weak ground, owing to poor consolidation. The case introduced here started from the necessity of taking measures against pollution, and is still practised now for recycling of wastes in automobile parts.
2. DECISION TO REUTILIZE
THE WASTE
The waste is generally discharged as a mixture and cannot be reused in its existing state. Reutilization of waste as a resource must start from its separation into constituent materials. It is not too much to say that a successful separation reaches halfway to successful reutilization as a resource. Examination of how wastes similar to ours (Fig. 1) are recycled in other industries showed that thick waste PVC leather discharged after the production of shoes and bags is separated into PVC grains and cloth by crushing and air classification, to reuse the PVC grains as a raw material for the product. By contrast, waste PVC leather and PVC urethane discharged from our plant comprises fragments generated in the production of car seats and interior products, and includes a large amount of thin cloth coated with thin PVC, most of which has urethane foam sewn together as a cushion. How to separate the mixture wastes efficiently into their constituent materials was a large problem, and examination started from this aspect. Concurrently, possible applications of recovered PVC and urethane were also examined, as described below. In general, the principal difficulty in the reutilization of wastes is the difficulty of maintaining continuity. One of the reasons concerns profitability, but a more serious fact is that demand continually changes, depending on the situation for the users of processed wastes. Processed waste suppliers wish demand to continue, but this is difficult to achieve. Therefore, our plant decided to use the wastes for our automobile parts with the greatest importance attached to continuity. 265
SEIJI MIYAMA
266
Glued (Waste PVC leather)
Soft urethane
(b)
foam
Cloth
Glued (Waste urethane)
I
Sewn (Waste PVC urethane)
Fig. 1. Kinds of wastes from seat production.
Examination reutilization
for
\
)
Examination on the method for separating constituent materials
Present flow
1
Fig. 2. Recycling flow. Materials to be crushed
Fig. 3. Crushing test equipment.
Successful research and development for the preparation of automobile parts from the waste took place under the cooperation of a parts maker. In addition, an efficient air separation and recovery device was developed, and regular operation began from 1975. The recycling system has been used from that date, although the applied parts, and the share of processing, have changed. Figure 2 shows the recycling flow.
RECYCLING OF WASTE PVC
261
Table 1. Experimental results of crushing Crushed quantity (kg) 17.0
Period of time (min) 8.0
Waste PVC urethane Waste PVC leather
13.2
Waste PVC urethane
No.
Sample Waste PVC leather
Crushing capability (kg hr-‘) 127
Crusher current (A) 20-30
Urethane pieces are too large.
13.5
58.6
20-30
Separation from PVC is poor.
19.0
10.0
114
30-50
If urethane can be blown away when held in the hand, then PVC can be easily separated.
7.0
8.0
52.5
30-50
Cloth adheres to PVC.
Crushed state
1
2
Waste PVC teather
/
and PVC urethane
-7
Feed convevor
YI
I 0
Cocyse ausher
I
Fan
thane chips
equipment
has
registered
in Japan.1
Fig. 4. Materials separation and recovery equipment flow.
3. EXAMINATION
OF THE METHOD FOR SEPARATING
MATERIALS
The wastes discharged from the shop include three types, as shown in Fig. 1. Of these, sewn three-layer articles (c) are generated in the largest quantities. Waste is no more than that, if it is not processed for separation into constituent materials. As for the methods for separating the constituent materials, for type (a), erosion of cloth by sulfuric acid is well known, but has not been used practically for (b) and (c) as far as we know. It was therefore necessary to develop a new separation method.
SEIJI MIYAMA
268
Waste PVC leather Waste urethane
Matertat
selecting
Waste cloth
f i ncinerated)
Fig. 5. Breakdown of recovered materials.
Table 2. Separation standard
Urethane
Specific gravity
Form
Recovered material
To be crushed into lo- 30 mm square pieces.
Purchased raw material (urethane 100%) - 0.02
To contain less than about 30 wt % of PVC and cloth.
Recovered material - 0.065
Chips
To be grains of 1 - 3 mm (the cloth adhering to the back of PVC may remain attached)
PVC Grains
Not to contain urethane.
Molded head rest
Moided arm rest FiUer for trunk mat
Fig. 6. Regions of applied parts (example).
It was concluded th# the most orthodox method, i.e. of ‘crushing and air separation* would be the optimum, on the precondition that the recovered constituent materials are not changed in the material.
269
RECYCLING OF WASTE PVC (a)
Molding of head rest and arm rest
Urethane
chips..
Worsted.. Binder..
(b) Production
.,
85% 10% 2
-
Mixing
Mold fiiling
-
_
_
Hot press
Product (I
of trunk mat
Table 3. Processed tonnage and recovered tonnage Kind of waste
output
Input
Kind of
465
Urethane chins
36%
t yr-’
PVC grains
72t
material Waste PVC leather
437tyr-’ Waste urethane
28 tyr-’ Waste PVC urethane
Waste cloth (incinerated)
Table 4. Annual processing cost
Depreciation Tax, interest and insurance
73.4 million yen 16.9 million yen 0.7 milhon yen
Sub-total Repair expenses Electric power charge Labor cost
17.6 million 3 .O million 3.4 million 10.8 million
Sub-total Total
17.2 million yen 34.8 million ven
Equipment investment Standing expenses cost Variable expenses
Unit cost of processing = ~~~~~~~~i$n~t
= 34’8 y$i,,
yen yen yen yen
yen * 80 yen kg-’
Separation tests
Based on the above conclusion, it was decided to make preliminary tests for obtaining data for determining the specifications of machines. (i) Samples. PVC film + cloth, glued (waste PVC leather). (PVC film + cloth) + (urethane + cloth), sewn (waste PVC urethane).
270
SEIJI MIYAMA Table 5. Amount of annual cost reduction, by material
cost Material used
Product cost When newly bought material is used
Annual consumption (2)
Annual cost reduction (1) x (2)
108 yen kg-’
365 000 kg
39.4 million yen
513 yen kg-’
Urethane When regenerated material is used When newly bought material is used
reduction per weight (I)
405 187 yen kg-’ 105 yen kg-’
PVC When regenerated material is used
72 OOOkg
7.6 million yen
82 Total
47.0 million yen
Overall effect Total annual cost reduction (Table 5) - Total annual processing cost (Table 4) = Effect. 47.0 million yen - 34.8 million yen = 12.2 million yen y-‘.
(ii) Crushing test equipment. Figure 3 shows the outline of the equipment. Crusher: rotary shear type, blade width 450 mm, with two fixed blades and five rotating blades, consumption 15 kW. Exhaust fan: turbo type, 23 m3 min-‘, 95 mm Aq, 0.75 kW. Recovery cyclone: barrel 600 diameter. (iii) Experimental results. As shown in Table 1, the recovery of urethane alone could be achieved by crushing only. However, the recovery of PVC required separation from the cloth, and it was found that actual operation required the additional use of a fine crusher.
4. OUTLINE OF THE MATERIALS
SEPARATION
AND RECOVERY EQUIPMENT
The following equipment was developed on the basis of the results of the above separation tests, considering workability, costs. Figure 4 shows the flowsheet. Process (i) Waste PVC leather and PVC urethane are put into a coarse crusher. Each piece should be about 300 mm square; larger pieces should be cut beforehand. (ii) The coarse crusher comminutes to 10 - 30 mm square pieces, and allows them to fall onto a vibrating conveyor. (iii) Air is sent from the underside of the vibrating conveyor, to agitate the crushed pieces. (iv) Light urethane chips are recovered by suction nozzles. (v) Heavy PVC is further crushed into 1 to 3 mm grains by fine crushers and recovered by a classifier. Breakdown of recovered materials The balance of the recovered materials is as in Fig. 5.
271
RECYCLING OF WASTE PVC
States of recovered materials If the waste PVC leather and PVC urethane were separated more accurately into the respective constituent materials, they would find wider application, but on the other hand, at a higher cost. Compromise is inevitable in this respect. Our plant uses the separation standards shown in Table 2. SELECTION
OF APPLICABLE
AUTOMOBILE
PARTS
The use of the processed waste for automobile parts is limited in application, and parts using the processed wastes should be the less-visible and less-functionally important. From this point of view, parts were examined by the value analysis technique, and the most suitable ones selected. Applied parts: Urethane chips: molded head rest and arm rest; PVC grains: filler for trunk mat. Figure 6 shows the regions of the applied parts. These parts were then molded, using the purchased raw materials only. As a matter of course, careful tests had been repeated by trial production for the parts, before regular production. The tests included: (i) Sensory tests for resiliency, cushioning, etc. (ii) Interlayer peeling tests between different materials. (iii) Durability tests. These tests were repeated to decide the optimum mixing ratios. 6. PRODUCTION
OF AUTOMOBILE
PARTS
The head rest, arm rest and trunk mat are produced according to the flow shown in Fig. 7. 7. QUALITY OF REGENERATED
MATERIALS
Provided that automobile parts display their proper commercial functions, it is of no importance whether they are made of purchased materials or regenerated materials. In our case, there was the rather unexpected result that the regenerated materials were better. For example, when a conventional product of urethane (100% purchased) needs a certain hardness, aggregate has to be added as required. However, the mixing of the regenerated material provides the proper hardness, eliminating the need for adding aggregate. As a considerable side effect, the cushioning property can be freely changed by changing the mixing ratio. 8. COSTS The actual statistics in our plant were as given below. (i) Processed tonnage and recovered tonnage are listed in Table 3. (ii) Annual processing costs are listed in Table 4. (iii) Annual cost reduction, by material, are listed in Table 5. The overall effect is (Total annual cost reduction) - (Total annual processing cost). Our plant achieves an annual positive effect of about 12.2 million yen. Including the expenses for land reclamation executed in the past, the effect corresponds to about 40 million yen.
212
SEIJI MIYAMA
9. CONCLUSIONS As described above, the reutilization of wastes in the plant began from the necessity of taking measures to prevent pollution; however, waste is now indispensably required as a raw material. The system is not, however, problem-free. In the past decade, the seats have been enhanced in quality, a drastic reduction in the use of PVC, and the use of woven fabric which is difficult to recycle, is increasing. In addition, the cost of solid moldings, using no regenerated material, has declined, causing severe competition with the regenerated materials. The reutilization of wastes as resources is not always simple. The recycling of wastes as a resource is always confronted by such difficulties. This case has the advantage that the regenerated materials are used for mass-produced motor vehicles, which provide a continuous demand. At our plant, we intend both to continue this project and to develop new applications.