PT105422A - MODIFIED CELLULOSE PULP, PREPARATION METHOD BY PROCESSING BY HIGH PRESSURE AND THEIR APPLICATIONS - Google Patents

Abstract

The present invention relates to the process for the modification of the properties of cellophane. THE PROCESS CONSISTES IN THE MODIFICATION OF CELLULOSIC PULLEY PROPERTIES THROUGH COLD / HOT PROCESSING BY HIGH HYDROSTATIC PRESSURE (100-1000 MPA) AT TEMPERATURES BETWEEN 0-100ºC DURING A TIME INTERVAL OF 1-75 MINUTES (MAY BE UPPER). THE PROCESSING APPLIES TO ANY TYPE OF CELLULOSIC PASTE, PREFERENTIALLY IN AQUATIC MEDIUM, WITH CONSISTENCY IN THE RANGE OF 0.1-40.0%. TREATED PASTES SUFFER STRUCTURAL ALTERATIONS AT THE LEVEL OF CELLULOSE AND INCREASE THE ACCESSIBILITY OF AMORFA CELLULOSE. THIS PROCESS IMPROVES THE HYDRATION OF THE PASTE, BY INCORPORATING WATER MOLECULES STRONGLY CONNECTED TO THE CELLULOSE. PROCESSING OF PREVIOUSLY DRY PASTA RESTORES ITS ABUSING CAPACITY, DECREASING THE PROBLEMS OF HORNIFICATION. STRUCTURAL CELLULOSE CHANGES INCREASE THE INTRINSIC STRENGTH OF FIBER, AND HYDRATION GIVES YOU GREATER FLEXIBILITY, ELASTICITY AND CONNECTION CAPACITY. THE PHYSICAL PROPERTIES OF THE PROCESSED PASTES BETTER THAN SIGNIFICANTLY, WITHOUT DECREASING THE HAND INDEX. IT IS SO POSSIBLE TO PRODUCE PASTES WITH DIFFERENT AND IMPROVED PROPERTIES, FOR VARIOUS APPLICATIONS, ESPECIALLY AS RAW MATERIAL FOR THE PAPER INDUSTRY OR EXCIPIENT IN THE CHEMICAL, FOOD AND PHARMACEUTICAL INDUSTRIES.

Description

Description " MODIFIED CELLULOSE PASTURES, PREPARATION METHOD BY PROCESSING BY HIGH PRESSURE AND THEIR APPLICATIONS "

The present invention relates to the processing of cellulosic pulps by high hydrostatic pressure for modification of their properties, which may have several applications.

This type of processing allows, among other effects, to incorporate water molecules tightly bound to the cellulose structure, imparting different and unique properties to the cellulosic pulps, which may have applications either in the production of paper with improved and different properties, or in obtaining improved products derived from the chemical modification of cellulose.

More specifically, the invention provides a method of modifying the properties of cellulosic pulps by hot / cold processing by high hydrostatic pressure (between 100-1000 MPa, but may be higher), at temperatures between 0 and 100øC for up to 75 minutes (may be higher), applicable to any type of cellulosic pulps with a consistency between 0.1 and 40%, preferably in an aqueous medium, but not only.

State of the art High pressure technology has been applied in the production of composite, ceramic and metallic materials (US 3,286,337), plastics and artificial diamond, and is currently an expanding technology that has attracted the attention of the food industry to processing and preserving foods (US 2004/0058041; US 3,407,721; US 5,213,029; US 6,217,435; US 5,932,272).

This technique, which currently operates at pressures between 100 and 1000 MPa, has been commercially used to modify the texture and to control microbial and enzymatic activity in foods without altering its nutritional and organoleptic properties. Cellulose is the most abundant polymer in nature, and can be used in its natural state or after chemical modification in a wide range of applications. Wood is one of the main industrial sources of cellulose, which can be used in the form of cellulosic pulp for the paper industry or as a raw material for the chemical industry. However, in the paper industry, during the pulp drying process, cellulose undergoes structural rearrangements at the level of the molecules present in the fibrils and in the areas of interfibrillar aggregation, causing a set of changes in the level of its physicochemical properties . As a consequence, the surface of the cellulosic fibers collapses, with a substantial decrease in their swelling capacity and a loss of flexibility. This phenomenon is known as hornification and is responsible for deteriorating the accessibility of cellulose to water and other chemical reagents, as well as for drastically reducing the paper properties of recycled pulps and fibers. A part of these changes are irreversible, i.e., the initial swelling properties of the fibers are not recovered after their rewetting and refining. This is one of the main problems that occur in the chemistry and technology of cellulose, 2 and that is not yet solved, causing significant costs to the paper industry and other industries. The modification of the properties of the cellulosic pulps by the method proposed in the invention, in particular by the hydration effect (incorporation of water molecules) also has applications at the level of the chemical reactivity thereof, with high potential for numerous applications.

Description The present invention aims at the modification of cellulosic pulps through hydrostatic high pressure processing and offers numerous potentialities not only for the pulp and paper industry but also for those industries that use pulp as raw material in modification reactions to obtain new products based on cellulose, such as the production of microcrystalline cellulose. The treatment by high hydrostatic pressure of the pulps promotes the addition of the cellulose crystallites through the cocrystallization and partial recrystallization of the paracrystalline domains on the surface of the elementary fibrils. This phenomenon is responsible for increasing the mean crystallite width (parameter d002, Table 1 and Figure 1). The rearrangement of the paracrystalline segments of the surface of the elementary fibrils causes an increase in the degree of crystallinity of the cellulose chains.

At the same time, hydrostatic high pressure processing causes hydration of the pastes, forcing the incorporation of water molecules that are strongly bound to the amorphous and inaccessible regions of the cellulose structure, and which are removed only at temperatures higher than 300 ° C. Thus, the hydration of the pulps promoted by the high hydrostatic pressure causes the fibers to regain some of their swelling capacity, causing the reduction of the effects of the firing on the dry pastes and giving greater flexibility and elasticity to the fibers. No other process is known to cause this effect, which is due to the particular nature of the operation of the high pressure hydrostatic technology, namely the high physical forces that it exerts on the processed products. Therefore, the treatment by high hydrostatic pressure extends the areas of use of cellulosic pastes that have been dried (including recycled pulps) and changes the properties of never-dried pastes.

After treating cellulose pulps by high pressure, paper sheets with a higher hand index (volume per unit weight of paper) and better properties of physico-mechanical resistance are obtained, as compared to sheets obtained from unprocessed pulps. This allows to obtain papers with more robust and diversified properties for the use of the final consumer (Figure 2), currently impossible to obtain by current industrial methods or described in the scientific literature. It is also worth noting that after hydration the reactivity of the cellulosic pulp increases, due to the increase of its accessibility to the interaction with chemical reagents, enabling new and improved chemical reactions.

These structural and hydration changes can be used for the chemical modification of cellulose for 4 different applications. As an example, hydrolysis with dilute sulfuric acid from slurries subjected to high hydrostatic pressure processing allows the amorphous portions of cellulose to be hydrolysed more rapidly and to a greater extent compared to pulp of unprocessed slurries by high hydrostatic pressure, or in pastes dried or dried pasta. Thus, the high pressure hydrostatic processing allows to obtain new products such as microcrystalline cellulose, providing not only products with different particle size, but also with a higher degree of crystallinity of the cellulose, with applications, for example as raw material for the paper industry or as an excipient in the chemical, food and pharmaceutical industries. The method of modifying cellulosic pulps object of this invention and described below may be applied to dry / never dried pastes, whether or not refined. 1. High pressure hydrostatic processing:

Prior to the treatment by high hydrostatic pressure, the cellulosic pulps are swollen in water for 0.5-24 hours, preferably under moderate agitation, in order to obtain suspensions with a consistency between 0.1-40.0%. After swelling, slurry suspensions are processed either cold or hot by high hydrostatic pressure (between 100-1000 MPa, but may be higher) at temperatures between 0 and 100øC for up to 75 minutes (and may be higher). Hydrostatic high pressure processing can be performed with the pastes in containers of varying size or geometry or mass. High pressure processing is applicable to any type of cellulosic pulps with a consistency of between 0.1 and 40.0%, preferably in aqueous medium, but not only. The steps for this modification to occur involve:

The step: swelling of the cellulosic pulps in water for 0.5-24 hours, preferably under moderate agitation, in order to obtain suspensions with varied consistencies; and second stage: after swelling, slurry suspensions are processed cold or hot by high hydrostatic pressure (between 100-1000 MPa, but may be higher) at temperatures between 0 and 100øC for up to 75 minutes (may be higher ). The treatment by hydrostatic high pressure of the pulps promotes the increase of the size of the cellulose crystallites, through the cocrystallization and partial recrystallization of the paracrystalline domains on the surface of the elementary fibrils, increasing the average crystallite width of the cellulose (parameter d002), as well as the increase of its degree of crystallinity. Simultaneously, the forced hydration caused by the hydrostatic high pressure treatments promotes the incorporation of water molecules that are strongly bound to the amorphous regions of the cellulose, increasing its accessibility for interaction with chemical reagents. In this way, with respect to the pulp currently present on the market, the structural alterations suffered by the pulp treated by high pressure cause it to present larger crystallites, with a higher degree of crystallinity, and its 6 fibers present a greater capacity of water absorption, as well as flexibility and elasticity. Due to the increased mechanical properties, a smaller amount of cellulosic pulp is required to achieve the same strength in the paper, which implies a saving of raw material. All these changes make the treated pulp become an excellent raw material not only for the production of paper with improved properties, but also for other applications such as new materials and for reactions of chemical modification of cellulose with various possible applications. 2. Acid hydrolysis

The advantages presented previously associated to the structural and hydration alterations of cellulosic pulps allow to improve the speed and extension of the reactions of chemical modification of the cellulose, for several applications. For example, if hydrolysis with dilute sulfuric acid is processed after the high hydrostatic pressure of the pastes (by the above method), it is possible to hydrolyze the amorphous parts of the cellulose more quickly and to a greater extent, processed by high hydrostatic pressure, either in pre-dried pastes or in dry pastes.

After processing by high hydrostatic pressure and drying, the slurry is swollen in water (at varying concentrations, typically 5% m / m). Acid hydrolysis takes place under reflux in the presence of dilute sulfuric acid in the range of 1.0 - 7.0M, preferably 1.8 Μ, for a time between 0.5-5h. After reaction and cooling, the mixture is filtered and washed with distilled water until a slurry with a pH of about 7. The slurry is then dried in the oven at 105 ° C to constant weight. The present invention proposes a process which consists in modifying the properties of cellulosic pulps by high pressure hydrostatic processing, applicable to any type of pastes preferably in aqueous but not in the same way, with consistency between 0.1 and 40.0%. The pulps thus treated undergo structural changes at the cellulose level (increase of the mean crystallite width), increase in the accessibility of amorphous cellulose and incorporation of water molecules bound to the cellulose, which improves the hydration of pulps. Processing pre-dried pastes restores their swelling ability, reducing burnout problems. The structural changes in cellulose increase the intrinsic strength of the fiber, and hydration gives it flexibility, elasticity and bondability, improving its physical properties without decreasing the hand index. The invention allows to produce pulps with different properties for various applications, such as in the production of paper with different and improved characteristics, in improved chemical modification reactions of cellulose, as well as for other applications.

The unprecedented results achieved with the high pressure processing of the cellulosic pulps, make this invention can be applied: i. The paper industry - the occurrence of kiln drying after drying the pulp is one of the reasons why it needs to be refined. However, this step represents significant energy expenditures in a manufacturing plant, which will be significantly reduced with the treatment by high hydrostatic pressure of the pastes. This application is due to the fact that the treatments by high hydrostatic pressure significantly reduce the problems of hornification due to the incorporation of water molecules that are strongly attached to the structure of the cellulose and remain there even after drying the pastes. This hydration also imparts a lot of flexibility to the fibers, making their mechanical strength properties much higher than those of untreated pulps. The hydration of the pastes is also reflected in terms of saving of raw material: it becomes possible to obtain papers with better physical and optical properties using less amount of fibers. ii. To the chemical industry specializing in cellulose products - increasing crystallite size and increasing crystallinity after treatment by high hydrostatic pressure, together with the increased accessibility of amorphous cellulose in the face of the attack of chemical reagents, are facts that make with which the cellulose processed by high hydrostatic pressure, brings together a set of unique characteristics that make it a better reagent to undergo chemical modification reactions in the cellulose processing industry in general.

Summary of the Invention The present invention relates to a process for the modification of cellulosic pulps comprising the following steps: a) disintegration and swelling of the pulp with water for 0.5 h to 24 h while stirring; b) pulp processing by high hydrostatic pressure, preferably between 100-1000 MPa which leads to the incorporation of tightly bound water molecules into inaccessible polysaccharide sites.

In a preferred embodiment step b) occurs at temperatures between 0-100 ° C for a time interval ranging from 1-75 minutes.

In another preferred embodiment the process is applicable to any cellulosic pulp having a consistency in the range of 0.1-40.0% and is also applicable to dry or never dried pastes, whether or not refined. The present invention further relates to the modified cellulosic pulps which are obtained by the process described above.

The cellulosic pulps of the present invention are used as paper pulps or for the manufacture of products for the chemical, food, pharmaceutical and biotechnology industries.

Examples

For an easier understanding of the invention, examples of preferred embodiments of the invention are described below, which, however, are not intended to limit the subject matter of the present invention. 10

Results obtained for two types of pulps (acid sulphite and kraft, among the several studied):

For this example the workup was carried out at a pressure of 400 MPa, for 10 min at 20øC, with a paste having a consistency of 5% (w / w).

For comparison, the results for unprocessed pulps are also presented.

Table 1 presents the parameters of the crystalline cellulose network of both pulps, before and after treatment by high hydrostatic pressure. The parameters a and b correspond to the unit cell dimension of the axes a and b shown in Figure 1, respectively; c represents the mean crystallite height, y represents the monoclinic angle formed and d002 the mean crystalite width in the network plane 002. The mean crystalite width increases with the high hydrostatic pressure processing, this being the most significant effect for the kraft pulp.

Table 1: Comparison of the crystalline cellulose network parameters in kraft and sulphite pulps, processed and unprocessed by high hydrostatic pressure.

(± 0.02 nm) b (± 0.02 nm) c (± 0.02 nm) □ (± 0.1 deg.) Do02 (± 0.1nm) Sulfite 0.801 0.790 1.033 93.3 4, 9 Sulfite + high pressure 0.800 0.788 1.033 93.6 2.6 Kraft 0.800 0.787 1.034 93.0 5.3 Kraft + high pressure 0.797 0.787 1.034 93.2 5.9

The main differences observed in the cellulose crystallite parameters occur at the average crystallite width, d002 - The changes obtained, for the same 11 operating conditions, depend on the type of pulp in question (pulp submitted to sulphite or kraft cooking). For the whole range of parameters tested the increase of the average crystallite width verified for sulphite pulps varied between 1-10%, while for kraft pulps the increase varied between 1-20%.

Table 2 shows the changes occurring at the level of the crystalline fraction of the cellulose present in the acid and kraft sulphite pastes, before and after treatment by high hydrostatic pressure, being evident the increase of the degree of crystallinity, index of crystallinity, and parameter of crystallinity pulp pulp, caused by high pressure hydrostatic processing.

Table 2: Degree of crystallinity, GC, index of crystallinity, IC, and parameter of crystallinity, PC, of pulp present in pulp before and after processing by high hydrostatic pressure, obtained by X-ray, 13C NMR and FTIR, respectively.

GC (± 0.3%) IC (± 1%) PC (± 1%) Sulfite 70.8 50 55 Sulfite + high pressure 73, 0 52 60 Kraft 72.7 45 53 Kraft + high pressure 76.5 50 The increase in the degree of crystallinity may range from 1.0 to 7.0% (determined by X-ray diffraction).

Table 3 shows the effect that the drying step exerts on the degree of burnification of a pulp, and the high pressure hydrostatic process allows the reduction of the drying of the dry pulp at 140 ° C 12 (temperature at which the drying of pulp in the pulp industry), to values close to those shown by the air dry pulp. However, this value is overestimated because the hornification is calculated by comparing the water absorption capacity of a paste that is never dry and dry, and in this case it is not possible to account for the water which, after processing at high hydrostatic pressure, is strongly bound to structure of the cellulose and which can only be released from the cellulose at very high temperatures, as mentioned above. Thus, the reduction of the occurrence of the cellulose firing effect of the pulp processed by high hydrostatic pressure will be even greater than the presented value.

Table 3: Effects of the different drying conditions and the treatment at high hydrostatic pressure in the furnace undergoing sulphite pulping.

Sulphite pulp Hornification (%) Never dry 0 Air dry 37 Dry at 140 ° C 43 Dry at 140 ° C and treated at high pressure 36

Figure 2 shows the mechanical behavior of paper sheets produced from a dry acid sulphite pulp, with and without high hydrostatic pressure treatment. It is evident that high pressure processing increases the mechanical strength properties (tensile strength, tearing, bursting and zero span tensions), as a result of the incorporation of water molecules strongly bound to the cellulose structure, which, in addition to giving greater flexibility to the fibers, reduce the effects caused by hornification.

After treatment at high hydrostatic pressure it is possible to obtain sheets of paper with increased mechanical strength properties. Increases in tensile strength were observed between 20-40%, bursting strength between 40-60% and zero span tensile strength between 10-20%. Regarding the tear strength, the increase verified ranged from 80 to 300%. High-pressure hydrostatic processing allows for chemical hydrolysis of the cellulose more rapidly and also more extensively, resulting in a greater amount of hydrolyzed cellulose.

Table 4 shows an example of the results obtained for the degree of crystallinity and mean width of crystallite, doo2i of the cellulose after hydrolysis. These two parameters increase with the pre-processing by high hydrostatic pressure.

Table 4: Comparison of mean crystallite width, d002, and degree of crystallinity, GC, of the cellulose present in a paste after hydrolysis.

Sulphite paste d002 (nm) GC (%) Never dried hydrolyzed for 3h 5.4 76.6 Dry at 140Â ° C hydrolyzed for 3h 5.36 76.9 Dry at 140Â ° C, treated at high pressure and hydrolyzed for 3h5 , 6 78.7

Description of Figures 14

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention, the following are attached figures which represent preferred embodiments of the invention which, however, are not intended to limit the subject matter of the present invention.

Figure 1 shows the X-ray diffractogram of the acid sulfite paste, with the representation of the respective amorphous and crystalline halos. Projection of the unit cell of the cellulose with the respective dimensions and network plans.

Figure 2 shows the mechanical behavior of sheets of paper produced from a dry acid sulphite pulp at 140 ° C, with and without high hydrostatic pressure treatment.

Figure 3 shows a forced hydration scheme of cellulose fibrils under high pressure effect.

References Patents: US 4,385, 172; 05/1983; Yasnovsky et al. ; Prevention of hornification of dissolving pulp. US 6,393,977 Bl; 05/2002; Ernest A. Voisin; Apparatus for pressure treating shellfish. US 5,932,272; 10/1968; Pierre Carvallo; Hydrostatic pressure type continuous sterilizing and cooling apparatus. US 5,213,029; 05/1993; Hideki Yutaka; Apparatus for treating food under high pressure. US 5,658,610; 08/1997; Cari Bergman et al .; Method and device in high-pressure treatment of liquid substances. 15 US 6,110,516; 08/2000; Dallas G. Hoover et al .; Process for treating foods using saccharide esters and superatmospheric hydrostatic pressure. US 6,217,435 Bl; 04/2001; Ernest A. Voisin; Process of elimination of bacteria in shellfish, of shucking shellfish and an apparatus therefor. US 2004/0058041 A1; 03/2004; Kevin S. Greenwald; Food Processing apparatus, method of preserving the food product and preserved food product. US 3,286,337; 11/1966; Charles Sauve; Processes for shaping metals under high hydrostatic pressure. US 3,329,535; 07/1967; Paul H. Langer et al .; Pressure treatment of superalloys and method of making turbine blade therefrom. US 5,932,272; 08/1999; Alois Raemy et al .; Process for preparing a food gel.

Articles:

Chen D, Guo Y, Huang RB, et al .; Pretreatment by ultra-high pressure explosion with homogenizer facilitates cellulose digestion of sugarcane bagasses; Bioresource Technology (2010), 101 (14): 5592-5600.

Kumar S, Gupta R, Lee YY, et al; Cellulose pretreatment in subcritical water: effect of temperature on molecular structure and enzymatic reactivity; Bioresource Technology (2010), 101 (4): 1337-1347.

The following claims further represent preferred embodiments of the present invention.

Lisbon, 16th January 2012 16

Claims (6)

A process for the modification of cellulosic pulps comprising the following steps: a) disintegration and swelling of the slurry with water for 0.5 h to 24 h with stirring; b) processing the paste by high hydrostatic pressure, preferably between 100-1000 MPa. Process for the modification of cellulosic pulps according to the previous claim, characterized in that it is applicable to any cellulosic pulp having a consistency in the range of 0.1-40.0%. A process for the modification of cellulosic pulps according to claims 1-2, characterized in that step b) occurs at temperatures between 0-100 ° C for a variable time interval of between 1-75 minutes. Process for the modification of cellulosic pulps according to claims 1-3, characterized in that it is applied to dry or never dried pastes, whether or not refined. Modified cellulosic pulps characterized in that they are obtained by the process described in claims 1-4. Use of the cellulosic pulps described in the preceding claim and obtained by the process described in claims 1-4 characterized in that they are used as paper pulps or for the manufacture of products in the chemical, food, pharmaceutical and biotechnology industries. Lisbon, January 16, 2012 2