Abstract
Nitrocellulose is one of the most important cellulose derivatives used in industry and commerce and one of the most important products of the chemical industry. Nitrocellulose is produced using the raw material alpha cellulose such as cotton linters pulp or dissolving wood pulp. For both raw materials, the appropriate form should be “fluff” or “mass”, which is used in the form of fluffy bales for cotton linters, and in the form of wood pulp, which is used in the form of sheets, which are first fluffed in a hammer mill and then nitrated. The aim of this research is to use a new method to reduce the size of wood pulp sheet. Then nitrated and produce commercial Nitrocellulose. In this study, an attempt is made to convert dense wood pulp sheets with a purity level of approximately 90% into chips and to produce Nitrocellulose by using a semi-industrial chopper, and finally to investigate the quality of the Nitrocellulose such as nitrogen percent, solubility, fineness, viscosity, thermal stability and resulted lacquer specification in terms of, turbidity, softness, color and transparency. In this study, the sheets were crushed and chipped using a chopper with pore size of 3 cm × 3 cm, 2.5 cm × 2.5 cm, 2 cm × 2 cm, 1.5 cm × 1.5 cm and 1 cm × 1 cm. Then, the chips were nitrated, separated additional acid boiled, milled and finally washed. The results showed that chips with a size of 3 cm × 3 cm are nitrated at the outer edges while no nitration occurs in the core and center of the chips. Reducing the size of the chips, the penetration of the chips improves, so that the best acid absorption can be observed with 1 cm × 1 cm chip. However, the main problem is that the amount of dust increases and the passing of fine particles through the filter increases. As a result, production yield decreases. Finally, the best pore size for chip production is 1.5 cm × 1.5 cm, which both increases the Capacity of chip production and enables better nitrating, and the passing of particles through the pores of the filter is very low. Thus, in this case, there are very few unnitrated particles, a lacquer turbidity of 11, appropriate softness, reasonable Bergmann stability of maximum 1.4 mgr., alkalinity of 0.01, acetone insolubility of 0.11 percent, and very few physical impurities. Also, the acid to cellulose ratio was reduced from 65/1 to 30/1 in the nitrator and from 25/1 to 15/1 in the autoclave compared to the fibrous state. Finally, the FT-IR graph shows that Nitrocellulose from the best chips exhibits a peak corresponding to the NO2 functional group and a peak corresponding to the OH functional group, which is very similar to those of Nitrocellulose from alpha cellulose cotton fiber. In GPC test average molecular weight Nitrocellulose resulted best chips (1.5 cm × 1.5 cm) was 55,303 Dalton and for Nitrocellulose produce from cotton linter pulp was 59,402 Dalton. The DSC showed that exothermic peak resulted of decomposition of Nitrocellulose from the best chips exhibits a peak in 202 °C which is very similar to those of Nitrocellulose from alpha cellulose cotton fiber (201 °C).
Keywords: Wood pulp, Alpha cellulose, Chips, Nitrocellulose, Nitrogen, Lacquer
Subject terms: Chemistry, Engineering, Materials science
Introduction
Environmental consciousness and the depletion of natural resources like fossil fuels, minerals, natural gas, etc. shifted attention towards renewable products. Among the naturally occurring structures, cellulose is one of the most versatile and abundant natural polymers, which can be obtained from different sources like plants, algae, bacteria, or tunicates. Cellulose (C6H10O5) is a linear polysaccharide consisting of a long chain of anhydroglucose units connected by β-1, 4 glycoside bonds. Nitrocellulose is a versatile material with a wide range of applications across various industries that derivate of cellulose polymer1–6. Nitrocellulose is one of the most energetic polymers that have extensive importance in many vital applications. Nitrocellulose has proven itself, since it was accidentally discovered, and until now as a pioneering material of great properties that can be used in different fields without faltering7–9. Nitrocellulose is one of the most important cellulose derivatives used in industry and commerce and one of the most important products of the chemical industry1,7,10–14. Its wide and varied use is mainly related to its special physical properties. The applications are mainly related to its relatively high elasticity and mechanical strength1,7,10–18. These properties result directly from the structure of cellulose, which consists of long chains of polysaccharide molecules. Not only Nitrocellulose, but all cellulose derivatives, such as other esters and cellulose ethers, exhibit a certain property14,19–23. Nitrocellulose has been used in many coating applications as well as part of the coating itself, a stabilizer, a membrane for the coating, and others. It is widely used in paints, lacquers, varnishes of wood, paper, and metal, inks for package printing, and celluloid printing. Recently Nitrocellulose used to produce of Paper-based Triboelectric Nano generator (P-TENG) is a way of generating a sustainable form of green electronics7. There are different types of Nitrocellulose, each with different physical properties and specific applications1,7,23–28. Cellulose fibers made from cotton linters pulp or high-purity dissolving cellulose fibers are used to produce Nitrocellulose. Linters pulp is usually in the standard form of pressed, fluffy bales of 150–200 kg. After opening the wrapping and the packaging wire, it is fed directly into the production line and used in the production process. However, Wood pulp is delivered to the world in the form of rolls or sheets and therefore cannot be used directly. It must therefore first enter the hammer mill, where the sheets are opened and convert to fluffy mass and then fed into the production line. Hammer mills have a number of disadvantages, such as high noise pollution, low safety, high speed of blade rotation, high dust generation, high electricity consumption, low capacity, fire hazard and need to an operator to feed the sheets into the miller. After fluffing the cellulose fibers, they are brought into the nitrating area for nitrating with the aid of a nitrator. With a ratio of mixed acid to alpha cellulose of 65/1, nitration takes 4 min. For further nitration, the substance is transferred to the post nitration, where further nitration is carried out for 36 min. Circulation and stirring processes are also carried out in this phase to complete the nitration. After nitration, the Nitrocellulose is placed in the excess acid separation pusher centrifuge so that the excess acid is separated from the Nitrocellulose and enters the spend acid tanks, and the Nitrocellulose obtained is mixed with water and placed in the dipping tanks. The Nitrocellulose is then transferred to the boiling autoclave to remove the remain excess acid from the fibers and to adjust the viscosity. The Nitrocellulose is also washed in several stages. boiling takes place in two stages at 120 °C for a total of 4–5 h. It is also washed 4 times with process water. After cooking and adjusting the viscosity to control the softness of the fibers, it is put into a conical miller to make the fibers finer and softener. Calcium carbonate is also added here to neutralize the acidity and remove the acid produced by cutting from the fibers. In the next stage, it is washed four times in a decanter so that particles and physical impurities rise to the top and are separated from there. Finally, it is dehydrated in a centrifuge and its moisture content reaches 30%. Then either alcohol is added and alcoholic Nitrocellulose is produced or a plasticizer is added, which is converted into Nitrocellulose granules after lacquering with ethyl acetate and finally dried in a fixed bed dryer, reducing its moisture content to below 1%. In a study entitled densified Nitrocellulose, in which they used as a raw material for commercial and military Nitrocellulose and found that by doing so they were able to produce Nitrocellulose chips29. They concluded that in this way the cost of transportation of the raw materials could be reduced, as well as the cost of transporting the Nitrocellulose. Other advantages of this plan included high product quality, high production safety, increased yield, energy savings and reduced environmental hazards. Mario pauquet and lan levac in 2023 investigated types of miller such as hammer mill, fixed hammer mill and cutter on Nitrocellulose quality and finally on resulting propellant. They have been resulted that if exist agglomerated or unfluffy fibers pieces, they cannot fully have nitrated and finally this agglomerated pieces remain in propellant matrix and has negative effect in properties of propellant especially ballistic performance burning rate, potential, mechanical properties and etc. also they have been showed that if milling and hitting (beating) of fiber was very much the yield of production will be decrease thus should be balance between agglomerated and fine fibers. Acacia pulp has been widely used in paper manufacturing industries since it contains cellulose with high cellulose content (above 92%). In a study conducted by Khai et al. both low-nitrated and high-nitrated Nitrocellulose were prepared using acacia pulp. FTIR spectra, nitrogen content, viscosity in acetone, thermal stability and dissolubility in organic solvents were examined for the synthesized Nitrocellulose. Also, a comparative study on the nitrogen content of Nitrocellulose obtained from acacia pulp and softwood cellulose was conducted. The conclusion of the study is that the distribution of nitrogen content of those Nitrocellulose is larger than that of Nitrocellulose from softwood cellulose29. As mentioned last paragraph Hammer mills have a number of disadvantages, such as high noise pollution, low safety, high speed of blade rotation, high dust generation, high electricity consumption, low capacity, fire hazard and need to an operator to feed the sheets into the miller. The aim of this project is replacing traditional fluffing method with a new technology of chipping sheet wood pulp in the producing of Nitrocellulose that doesn’t have these disadvantage and has more advantage in Nitrocellulose producing.
Experimental section
Materials
Alpha cellulose with a purity of 98.90% was obtained from Linter Pak Behshahr Company. Also, in order to accomplish the nitration process on alpha-cellulose fibers, the sheet wood pulp imported from UPM company of Finland (as Table 1) and the mixed acid was prepared from Karoon Petrochemical Company with compositions as Table 2 (see in Fig. 1).
Table 1.
Specifications of the wood pulp.
| Typical value | Spec | |
|---|---|---|
| Brightness, ISO % ISO 2470-1 | 89 | ≥ 88 |
| Impurities, mm2/kg ISO 5350 | 3 | – |
| Extractives, % ISO 1762 | 0.04 | ≤ 0.15 |
| Ash content, % ISO 1762 | 0.1 | ≤ 0.2 |
| pH ISO 6588 | 5.7 | 5.0–7.0 |
Table 2.
Number of components in the mixed acid.
| Acid type | Amount | Purity percentage |
|---|---|---|
| Nitric acid | 22.70–22.90 | 98% |
| Sulfuric acid | 60.20–60.40 | 98% |
| Water | 17.00 | Distillated water |
Fig. 1.
Sheets of wood pulp (left), alpha cellulose (center), mixed acid (right).
The sheet thickness is 1 mm, the sheet density is 1100 g/cm3 and the sheet dimensions are 75 cm × 75 cm. A mixed acid was used to nitration process the wood pulp chips and alpha cellulose fibers in the amount shown in the Table 2.
A semi-industrial chopper with meshes with different openings was used to shred the sheet: 3 cm × 3 cm, 2.5 cm × 2.5 cm, 2 × 2 cm, 1.5 cm × 1.5 cm and 1 cm × 1 cm (As seen in Fig. 2). The specifications of the device are: Power: 20 HP, 75 KW, Speed: 140 rpm and Inlet opening width: 80 cm.
Fig. 2.
Industrial chopper. (A) Chopper, (B) Screen (C) operation of chipping, (D) blade.
Nitrator equipment: Nitration was first carried out in a 2-L laboratory nitrator and then in a 10-L glass Nitrator at a temperature of 29 
for a total of 40 min using a stirrer on two levels (As seen in Fig. 3).
Fig. 3.
10-L glass laboratory nitrator (right), 2- liter nitrator (left).
After nitration, the excess acid is drained off with vacuum filter and the resulting Nitrocellulose is washed with hot water. After washing and deacidification, the Nitrocellulose is transferred to a Boiling autoclave and boiled at 120 °C in two stages for 2 h and then washed. In the next stage, the resulting Nitrocellulose is milled with a laboratory PFI refiner and neutralized with calcium carbonate (As seen in Fig. 4). Then washed in a decanter in 5 stages and finally dehydrated using a vacuum filter. The resulting Nitrocellulose is dissolved in the solvents ethanol and ethyl acetate and processed into lacquer. The turbidity of the resulting lacquer is measured using a refractometer. Nitrogen content calculated using the Kjeldahl or titration methods. The Bergmann thermal stability and insolubility of Nitrocellulose in acetone determined using the Abel and standard method30. Nitrocellulose and lacquer were characterized using standard procedures, namely nitrogen percent with ASTM D301 and ASTM D4795-94 (2003), solubility with ASTM D365-1, turbidity with ASTM D 7315-17, fineness with ASTM D8394-21, and Bergmann with ASTM-DTL-244C.
Fig. 4.
5- liter boiling autoclave (left), PFI Miller (center), vacuum filter (right).
Results and discussion
The operational tests that can be evaluated in the final Nitrocellulose and lacquer sample are opacity, nitrogen content, stability and the presence or absence of physical impurities in the lacquer, which were compared with a lacquer sample obtained from fluffy cotton linters alpha cellulose (As seen in Fig. 5). All analyzes were performed and reported with a repeatability of at least 3.
Fig. 5.
Types of cellulose chips and their sizes.
Investigation of the influence of chips size on the properties of Nitrocellulose and lacquer
Here, the pores size of the chopper and the size of the resulting chips on the properties of Nitrocellulose fibers and lacquer were investigated and compared to the control sample of cotton-linters alpha cellulose fibers (see in Table 3).
Table 3.
Effect of the size of the chopper mesh pores and the size of the resulting chips on the properties of Nitrocellulose and lacquer fibers.
| Specification | Chips size (cm) | |||||
|---|---|---|---|---|---|---|
| 3 × 3 | 2.5 × 2.5 | 2 × 2 | 1.5 × 1.5 | 1 × 1 | Control | |
| Nitration | Incomplete | Incomplete | Incomplete | Complete | Complete | Complete |
| Turbidity | 25 | 22 | 15 | 12 | 12 | 10 |
| Stability | Unstable | Unstable | Stable | Stable | Stable | Stable |
| Nitrogen | 10.15 | 10.25 | 11.35 | 11.55 | 11.60 | 11.65 |
| Insoluble in acetone | 0.21 | 0.18 | 0.15 | 0.12 | 0.10 | 0.10 |
| Viscosity | Unmeasurable | Unmeasurable | Unmeasurable | Type 31 | Type 31 | Type 31 |
As can be seen from Table 3, the nitration reaction is not fully completed in cellulose chips 3 cm × 3 cm, 2.5 cm × 2.5 cm and 2 cm × 2 cm the nitration reaction, so it can be clearly seen in the Fig. 6 that there is live sheet in the central part of the chips in these dimensions, the fibers in center is remain unnitrated, while the edge areas are fully nitrated. One of the reasons for the nitrating in the edge area is that when the blades hit this area during the chipping process, more beatings are applied to the surface in the form of crushing, which causes the blades to open in these areas. It is also observed that by reducing the dimensions of the chips to 1.5 cm × 1.5 cm and 1 cm × 1 cm, due to the reduction in the size of the chips and the more crushing to surface of the sheets, these chips take on a puffy and open state, causing complete nitrating of these two types of chips. It is also observed that in chips with dimension 3 cm × 3 cm, 2.5 cm × 2.5 cm and 2 cm × 2 cm, the turbidity of the resulting lacquer increases due to the lack of complete nitrating and the presence of non-nitrated particles, while for samples with dimensions of 1.5 cm × 1.5 cm and 1 cm × 1 cm, a uniform and transparent lacquer is obtained due to complete nitrating. Figure 7 shows Nitrocellulose samples prepared from cellulose chips of different sizes, and Fig. 8 shows the color and turbidity of lacquer samples prepared from Nitrocellulose derivate from cellulose chips of different sizes. In addition, incompletely nitrated samples will be unstable and fully nitrated samples will be stable. On the other hand, the percentage of nitrogen in incompletely nitrated samples is low because they are not fully nitrated and vice versa. In addition, the percentage of insoluble substances is higher in larger samples and lower in smaller and fluffier samples.
Fig. 6.
Nitration of chips with different sizes, that are not fully nitrated in the large size specially in center of the chips.
Fig. 7.
Nitrocellulose samples made from cellulose chips of different sizes. (A) 3 cm × 3 cm, (B) 2.5 cm × 2.5 cm, (C) 2 cm × 2 cm, (D) 1.5 cm × 1.5 cm, (E) 1 cm × 1 cm, (F) Nitrocellulose Resulted of alpha cellulose.
Fig. 8.
Color and turbidity of lacquer samples made from pulp chips of different sizes. (A) 3 cm × 3 cm (B) 2.5 cm × 2.5 cm (C) 2 cm × 2 cm (D) 1.5 cm × 1.5 cm (E) 1 cm × 1 cm, (F) alpha cellulose.
The milling process was therefore also carried out on Nitrocellulose (both fully and not fully nitrated). As can be seen, the finished Nitrocellulose has the form of fluffed fiber as a result of the milling. However, these fluffed mass will not be a proof of the high quality of the Nitrocellulose. This is because with dimensions of 3 cm × 3 cm, 2.5 cm × 2.5 cm, 2 cm × 2 cm, since the central part has not been nitrated, we have a powder with a much lower nitrogen content that does not dissolve in the solvent and remains in the paint, ink, lacquer and in the form of non-nitrated particles or fibers or fluff.
FTIR result
As seen in Fig. 9A and B, the FT-IR of Nitrocellulose prepared of wood pulp with 89% purity from chips with 1.5 cm × 1.5 cm size (best chips size) is similar to Nitrocellulose prepared of cotton linters with 98% purity. In this graph wave number 850 and 3500 related to OH group and 1250 and 1650 related to NO2 group. Also, can see the intensity of NO2 group peak is very much and OH group is very low, this is show that most of OH group of cellulose replaced with NO2 group and formed Nitrocellulose completely31.
Fig. 9.
FT-IR of Nitrocellulose prepared of (A) wood pulp with 89% purity from chips with 1.5 cm × 1.5 cm size. (B) Cotton linters with 98% purity.
As seen in Fig. 10A and B, the FT-IR of Nitrocellulose prepared of wood pulp with 89% purity from chips with 2.5 cm × 2.5 cm size is different to Nitrocellulose prepared of wood pulp with 89% purity from chips with 1.5 cm × 1.5 cm size and cotton linters with 98% purity. In this graph wave number 850 and 3500 related to OH group and 1250 and 1650 related to NO2 group. Also, the intensity of NO2 group peak is not much and OH group is much, this is show that few of OH group of cellulose replaced with NO2 group and formed incompletely Nitrocellulose.
Fig. 10.
FT-IR of (A) wood pulp with 89% purity from chips with 1.5 × 1.5 cm size. (B) Nitrocellulose prepared of wood pulp with 89% purity from chips with 2.5 × 2.5 cm size.
GPC result
As seen in in Fig. 11A and B, the GPC of Nitrocellulose prepared of wood pulp with 89% purity from chips with 1.5 cm × 1.5 cm size (55,303 Dalton) is closer to Nitrocellulose prepared of cotton linters with 98% purity (59,402 Dalton). Polydispersity is a standard for uniformity of Nitrocellulose. Whatever it closer to 1, molecular weight distribution of polymer is good and vice versa. Accordingly seen the polydispersity of Nitrocellulose from chipping wood 1.5 cm × 1.5 cm is 8.2 and Nitrocellulose from alpha cellulose cotton linter pulp is 3.5.
Fig. 11.
GPC of Nitrocellulose prepared of (A) wood pulp with 89% purity from chips with 1.5 × 1.5 cm size. (B). Nitrocellulose prepared of cotton linters with 98% purity.
DSC result
As seen in Fig. 12A and B, the DSC of Nitrocellulose prepared of wood pulp with 89% purity from chips with 1.5 cm × 1.5 cm size is closer to Nitrocellulose prepared of cotton linters with 98% purity. If peak of thermal decomposition of Nitrocellulose less than 180 
it is sensitive to heat and if it was upper than 180 
it’s sensitive is the range of standard. As seen the below graph, the peak of exothermic is upper than 180 
and they are insensitive.
Fig. 12.
DSC of Nitrocellulose prepared of (A) wood pulp with 89% purity. (B). Cotton linters with 98% purity.
Investigation of the effect of wood chips size on production yield in a Nitrator
Here, the effect of using cellulose in the form of chips was compared with fluffy cotton linter fibers on the production yield in a nitrator (see in Table 4).
Table 4.
Effect of using cellulose in the form of chips and fluffy cotton linters fibers on production yield in the nitrator.
 Ratio |
Chips size (cm) | |||||
|---|---|---|---|---|---|---|
| 3 × 3 | 2.5 × 2.5 | 2 × 2 | 1.5 × 1.5 | 1 × 1 | Control | |
 |
ok | ok | ok | ok | ok | ok |
 |
ok | ok | ok | ok | ok | ok |
 |
ok | ok | ok | ok | ok | Not ok |
 |
ok | ok | ok | ok | Not ok | Not ok |
 |
ok | ok | ok | ok | Not ok | Not ok |
 |
ok | ok | ok | Not ok | Not ok | Not ok |
As mentioned in the reference and Nitrocellulose plants, the ratio of mixed acid to cellulose for nitration is normally 
for cellulosic mass in the form of fluff, but this proportion can be reduced by using cellulosic masses in the form of chips. As can be seen, this proportion can be reduced to 
and nitrating can be carried out. However, for chips with dimensions of 3 cm × 3 cm, 2.5 cm × 2.5 cm, 2 cm × 2 cm, this is not desirable because the center part are not nitrated, and the maximum proportion is 
, which is desirable. For chips up to 
and for cotton-linters cellulose fibers, it is 
, which is due to the nature of fluffy form and the openness of the cellulose mass, which is bulky and cannot be used below 
for linters cellulose and 
for 1 × 1 cm chips. However it can be concluded that, in the best case, a reduction from 
to 
is possible when using cellulose chip technology, in the other hand the nitrating capacity in a 2 m3 nitrator increases from 25 to 65 kg per batch, i.e. the production capacity in the nitrator increases by a factor of 2.5.
Investigation of the influence of chips size on production yield in an autoclave
In this section, the effect of cellulose chip size on the yield of Nitrocellulose production in an autoclave has investigated. As can be seen in Table 5, the ratio of water to Nitrocellulose in the Nitrocellulose plant is 
. By using cellulose in the form of chips, this ratio can be reduced from 
to 
. The proportion of 
is also not suitable for any of the dimensions of chips and linters cellulose fibers. This is because their degree of consistency is very much, and washing, dewatering, viscosity adjustment and the removal of acids from the inside of the nitro cotton fibers are made more difficult. Therefore, the best ratio is 
for chips with dimensions of 3 cm × 3 cm, 2.5 cm × 2.5 cm, 2 cm × 2 cm. However, best ratio is 
for 1 cm × 1 cm size and 
for linter cellulose fibers. Since the nitrating quality is low for chips with dimensions of 3 cm × 3 cm, 2.5 cm × 2.5 cm, 2 cm × 2 cm, these dimensions are not suitable, and cellulose chips of 1.5 cm × 1.5 cm are the best in terms of product quality and production yield in the autoclave. With the technology of using cellulose in the form of chips, especially with the dimensions of 1.5 cm × 1.5 cm, the production capacity of Nitrocellulose in the autoclave can be increased by a factor of 3 times. In other words: In an autoclave of 20 m3, the production capacity can be increased from 700 to 1900 kg per batch.
Table 5.
Effect of cellulose chips size on the production yield of Nitrocellulose in autoclave.
 ratio |
Chips size (cm) | |||||
|---|---|---|---|---|---|---|
| 3 × 3 | 2.5 × 2.5 | 2 × 2 | 1.5 × 1.5 | 1 × 1 | Control | |
 |
ok | ok | ok | ok | ok | ok |
 |
ok | ok | ok | ok | ok | ok |
 |
ok | ok | ok | ok | ok | Not ok |
 |
ok | ok | ok | ok | Not ok | Not ok |
 |
ok | ok | ok | ok | Not ok | Not ok |
 |
Not ok | Not ok | Not ok | Not ok | Not ok | Not ok |
Investigation of the effect of chips size on production yield in the filtering
Here, the effect of chip size on retention or passage through the filtering slot was investigated and compared with the control sample of long-staple cotton linters cellulose (see in Table 6).
Table 6.
Effect of cellulose chip size on retention or passage through the filter pore.
| Chips size (cm) | 3 × 3 | 2.5 × 2.5 | 2 × 2 | 1.5 × 1.5 | 1 × 1 | Control |
|---|---|---|---|---|---|---|
| Passing through a filter | Remained | Remained | Remained | Remained | Passed | – |
Since the length of wood pulp fibers are 2 to 3 mm and for alpha cellulose fibers are 10 mm, the pulp fibers inherently tend to pass through the 120-micron pore of the vacuum filter due to their small size. As shown in the Table 6, cellulose chips with a size of 3 cm × 3 cm, 2.5 cm × 2.5 cm, 2 cm × 2 cm and 1.5 cm × 1.5 cm remain in the filter and do not enter the waste acid. However, the 1 × 1 cm sample is ejected from the slot and enters the waste acid due to the fluff and small size of the fibers. According to the above, the best dimensions for Nitrocellulose production are 1.5 × 1.5.
Investigation of the influence of chip size on the yield of chip production
In this section, the effect of cellulose chip size on chopper production yield has investigated. It was found that the larger the cellulose chips, the higher the production capacity of the chopper and the higher the production Yield. When the size of the chips is reduced, the production Yield decreases to 85%, which means that by reducing the size of the chopper pores, the number of collisions of the blades of the device to chips increases and more dust particles are generated, which ultimately leads to a decrease in production Yield (see in Table 7).
Table 7.
Effect of the size of the cellulose chips size on the yield of the chopper.
| Chips size (cm) | 3 × 3 | 2.5 × 2.5 | 2 × 2 | 1.5 × 1.5 | 1 × 1 | Control |
|---|---|---|---|---|---|---|
| Production yield percentage | 97 | 95 | 93 | 92 | 85 | – |
Investigation of the effect of chip size on the production of fine particles and dust
In this section, the effect of the pore size of the chopper on the production of cellulose particles and dust has investigated. As can be seen from Table 8, the smaller the pore size of the chopper, the more dust is produced. This dust is made of cellulose, but since it is fine and tiny, after nitrating it comes out of the slot in the filter section, which reduces the production yield of the factory.
Table 8.
Effect of chopper pore size on the production of cellulose particles and dust.
| Chips size (cm) | 3 × 3 | 2.5 × 2.5 | 2 × 2 | 1.5 × 1.5 | 1 × 1 | Control |
|---|---|---|---|---|---|---|
| Percentage of dust particles | 3 | 5 | 7 | 8 | 15 | – |
Investigation of the effect of chip size on the cost price of the Nitrocellulose
Table 9 shows the effects of chip size on the cost price of Nitrocellulose. As can be seen, the price of wood pulp is half that of alpha cellulose cotton linter. In addition, the quality of Nitrocellulose lacquer is suitable for grade E and some grade A. As can be seen from Table 9, the cost of Nitrocellulose is 1.4 $, assuming that the best quality of Nitrocellulose and lacquer is obtained from chips with dimensions of 1.5 cm × 1.5 cm, the cost price of Nitrocellulose will be 1.4 $, while the cost of Nitrocellulose with alpha cellulose-cotton linters is 2.7 $.
Table 9.
Effect of pulp use and chip size on the cost price of Nitrocellulose products.
| Chips size (cm) | 3 × 3 | 2.5 × 2.5 | 2 × 2 | 1.5 × 1.5 | 1 × 1 | Control |
|---|---|---|---|---|---|---|
| Cost price ($) | 1.3 | 1.3 | 1.3 | 1.4 | 1.6 | 2.7 |
Investigation of the effect of chip size on production yield
In this section, the effect of pulp chip size on the production yield of Nitrocellulose per unit of Nitrocellulose is presented and compared with the control sample of cotton linter alpha cellulose. As can be seen in Table 10, the percentage purity of the pulp in terms of cellulose (approximately 90%) is lower than that of cotton linter cellulose (98%), i.e. hemicellulose, beta-cellulose and gamma-cellulose are present. These compounds are nitrated in the same way as cellulose, but increase the opacity of the resulting lacquer. In addition, some of the cellulose-like compounds dissolve in the mixed acid, which reduces the yield of Nitrocellulose production from cellulose pulp. If we also take into account that the cellulose sheets generate dust due to the beating and chopping of the chopper blades, this results in yield of 88% for the best sample of 1.5 cm × 1.5 cm.
Table 10.
Effect of pulp chip size on Nitrocellulose production yield per unit of Nitrocellulose.
| Chips size (cm) | 3 × 3 | 2.5 × 2.5 | 2 × 2 | 1.5 × 1.5 | 1 × 1 | Control |
|---|---|---|---|---|---|---|
| Production yield | 90 | 90 | 89 | 88 | 84 | 98 |
| Hemicellulose content | 10 | 10 | 10 | 10 | 10 | 0.5 |
Conclusion
This study investigated the use of new technologies and conventional raw materials in the production of commercial E Grade Nitrocellulose. The important aim is to evaluate the use of cellulose sheets processed into chips compared to traditional fluffing methods in the production of commercial E Grade Nitrocellulose, with a focus on production yield, safety, environmental impact, and cost reduction. In this study, it was investigated that the conversion of cellulose sheets is converted into chips using a chopper, they have more advantages than fluffing with a hammer mill. It was investigated that the best dimensions for chips are 1.5 cm × 1.5 cm, so that they have the lowest dust generation, high production yield in the shredder, high safety and a lower environmental impact. In addition, the best quality for Nitrocellulose fibers and lacquer was achieved with these dimensions. Finally, the FT-IR graph shows that Nitrocellulose from the best chips exhibits a peak corresponding to the NO2 functional group and a peak corresponding to the OH functional group, which is very similar to those of Nitrocellulose from alpha cellulose cotton fiber. This show that cellulose converted to Nitrocellulose with NO2 group instead OH group. In GPC test average molecular weight Nitrocellulose resulted best chips (1.5 cm × 1.5 cm) was 55,303 Dalton and for Nitrocellulose produce from cotton linter pulp was 59,402 Dalton that the peak of them is similar with together. The DSC showed that exothermic peak resulted of decomposition of Nitrocellulose from the best chips exhibits a peak in 202 °C which is very similar to those of Nitrocellulose from alpha cellulose cotton fiber (201 °C). It can be concluded that, in the best case, a reduction acid / cellulose ratio from 
to 
is possible when using cellulose chip technology, i.e. the nitrating capacity in a 2 m3 nitrator increases from 25 to 65 kg per batch, i.e. the production capacity in the nitrator increases by a factor of 2.5. With the technology of using cellulose in the form of chips, especially with the dimensions of 1.5 cm × 1.5 cm, the production capacity of Nitrocellulose in the autoclave can be increased by 3 times. In other words: In an autoclave of 20 m3, the production capacity can be increased from 700 to 1900 kg per batch. In the separation excess acid stage with filter, the passage of the fibers through the pore was reduced compared to the fluffy state. Cellulose chips with size of 3 cm × 3 cm, 2.5 cm × 2.5 cm, 2 cm × 2 cm and 1.5 cm × 1.5 cm remain in the filter and do not enter the waste acid. However, the 1 × 1 cm sample is ejected from the slot and enters the waste acid due to the fluff and small size of the fibers. According to the above, the best dimensions for Nitrocellulose production are 1.5 × 1.5. Commercial wood pulp is available worldwide in large quantities for the production of various types of paper, cardboard, paper towels, baby diapers, sanitary napkins, etc., and its supply is not limited in any country. Its cost is also much lower than that of dissolving wood pulp, so the cost of Nitrocellulose (E Grade) will be lower by the same amount. The cost of Nitrocellulose is 1.4 $, assuming that the best quality of Nitrocellulose and lacquer is obtained from chips with dimensions of 1.5 cm × 1.5 cm, the cost price of Nitrocellulose will be 1.4 $, while the cost of Nitrocellulose with alpha cellulose-cotton linters is 2.7 $
Author contributions
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by all authors.
Funding
This research was supported by university of Zabol (Iran) with grant code (IR-UOZ-GR-5071).
Data availability
The data supporting this study are available when reasonably requested from the corresponding author.
Declarations
Competing interests
The authors declare no competing interests.
Footnotes
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Contributor Information
Ali Khalili Gashtroudkhani, Email: a.khalili@ippi.ac.ir.
Mohammad Dahmardeh ghalehno, Email: mmdahmardeh@uoz.ac.ir.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data supporting this study are available when reasonably requested from the corresponding author.