JPH0621183B2 - Cellulose dope and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cellulose dope and a method for producing the same.

2. Description of the Related Art Generally, a regenerated cellulose molded product is prepared by dissolving cellulose in a solvent by a certain method, and then using the extruder to form the dope.
It is produced by charging in a non-solvent or a regenerated solvent. At present, the only methods of dissolving cellulose that are industrially used for the above purposes are the copper ammonia method and the viscose method, which were discovered in the end of the 1890s. The cellulose in the dope obtained by these methods is characterized in that the cellulose is not dissolved as it is, but as a certain type of cellulose derivative. Therefore, in order to return to cellulose, a so-called regeneration operation is necessary. Moreover, there are many problems in the process of producing any of the above-mentioned dopes and in molding from the dopes, from the viewpoint of working environment such as discharge of heavy metals and generation of toxic gas, and also from the viewpoint of pollution. In addition to this, although not industrially used, as a method for dissolving cellulose, metal complexes such as cadmium (cadmium / ethylenediamine / alkali) and cooxene (cobalt / ethylenediamine /
Alkali), Zincocene (Zinc / Ethylenediamine / Alkali), Nioxene (Nickel / Ethylenediamine /
Alkaline) and EWNN (iron / tartaric acid / alkali) are known. However, none of them surpasses the copper-ammonia method or the viscose method in terms of using toxic components such as heavy metals and amines and in terms of economy. In particular, the viscose method using carbon disulfide, in the current regenerated cellulose industry,
Although overwhelmingly adopted by many companies, there are voices in the US and Europe worried about the industrial viability of the viscose method from the above viewpoint. The notable manifestation is the withdrawal of many companies from the viscose business (rayon business) in the 1960s and 1970s. As a reflection on these industrially existing dissolution methods, cellulose is directly dissolved in an organic solvent,
Since the 1970s, research has been conducted mainly in Canada and the United States to try to obtain a new regenerated cellulose molded product by closing the fiber or membrane manufacturing process. As a result, many dissolution methods have been found, but all of them are methods using a complicated multi-component solvent, and the cost of the solvent itself is high,
At present, there are no practical examples due to toxicity, explosiveness, difficulty of recovery, etc. Furthermore, most of the newly discovered dissolution methods of cellulose are that the cellulose is in the form of a certain derivative, and the derivative is dissolved in an appropriate solvent. It was just an idea that was not much different from. For example, in the case of the dimethylsulfoxide method, cellulose is dissolved as methylol cellulose, and in the dimethylformamide / N ₂ O ₄ method, it is dissolved as cellulose nitrite. The same applies to the SO ₂ / amine method and the dimethylformamide / chloral method. As can be seen from the history of such cellulose dissolution technology, it is extremely difficult to dissolve cellulose in a simple and inexpensive solvent.

On the other hand, cellulose has a degree of polymerization (hereinafter referred to as "DP").
Is extremely small (eg DP = 10), it is known that alkali and of course dissolve in hot dimethyl sulfoxide. Its degree of polymerization is 20 or less, and it cannot be used because it does not have sufficient mechanical properties as a cellulose molded product. The reason why the extremely low degree of polymerization cellulose is soluble in alkali or the like is that the characteristic polymer property of cellulose, for example, the molecular morphology defined by hydrogen bond is lost. It is also well known that an aqueous solution of caustic soda in the vicinity of 10% by weight has a strong swelling action on cellulose having a high degree of polymerization. Journal of Prake. Chem., NF, 15
8 , 233 (1941), the solubility of natural cellulose, mercerized cellulose, and reprecipitated (probably regenerated) cellulose in a 10 wt% caustic soda aqueous solution is shown. Although there is no description of dissolution conditions, polymer concentration, etc.,
According to this, the degree of polymerization (D
P) = 400 until DP = 120 for reprecipitated cellulose
It is said to be soluble up to 0. However, it is expected that these descriptions include considerable arbitrariness and also included a gel which was swollen but strongly swollen. As a result of additional tests by the present inventor, the solubility of cellulose in 10% by weight of caustic soda at −5 to 5 ° C. is affected by the polymer concentration and the degree of polymerization. For example, in the case of natural cellulose (cotton linter) with DP = 360, centrifugation is performed. Separation (20,000 revolutions,
46 minutes) When the operation of removing the L gel was carried out, the whole was not dissolved even at a polymer concentration of 0.5%. Therefore,
Journal of Prakt. Chem., NF, 158 , 233 (194
The meaning of "soluble" in the description of 1) is judged to be a gel containing a low concentration and is not industrially applicable. These points are due to the fact that alkali was used for the fractional dissolution of cellulose in each lateral order (for example,
"Purification and chemical reaction of polymer", P128-132.
It is also known from the Society of Polymer Science, edited by Kyoritsu Shuppan, 1933). This is an operation to divide into an alkali-soluble part and an insoluble part, depending on the molecular weight of cellulose and the aggregation state of molecular chains.
The former melted part includes the gel. These facts show that most of the highly polymerized celluloses that one wants to dissolve are
It shows that it is technically extremely difficult to dissolve the cellulose at a concentration of 00% and to dissolve the cellulose at a high concentration in an alkali having a single composition. In fact, in the history of the cellulose industry, such cellulose / alkaline solutions have never been used as molding dopes.

The present inventors consider the drawbacks of the dissolution method currently being industrially performed as described above, the idea of the organic solvent method, and the like, and change the molecular structure of the cellulose to make the cellulose cheaper and simpler. The present invention has been achieved as a result of earnest studies for dissolution in water.

Problems to be Solved by the Invention: The present invention is an alkaline aqueous solution dope of cellulose which has a relatively high degree of polymerization and dissolves in an alkali at low temperatures, and also causes problems from an economical and pollution standpoint. It is an object of the present invention to provide a cellulose dope capable of being used for the production of excellent fibers, membranes and other molded articles, applied to the surface and the inside of other materials, or immersed in other materials, and a method for producing the same.

Means for Solving the Problems: In one aspect thereof, the present invention is an alkaline aqueous solution dope of cellulose containing substantially 3% by weight or more of a cellulose having a degree of polymerization of 100 or more, and in its ¹³ C-NMR spectrum, carbon peaks of C ₄ position to provide a cellulose dope suitable for stable and molding characterized in that it is found in high field than 7ppm than the C ₄ position carbon peak of solid cellulose-based strong intramolecular hydrogen bond.

In another aspect of the present invention, 100 parts by weight of cellulose having an arbitrary crystal type and a hydrogen bond cleaving solution 10 to 10 are used.
100 parts of a mixture of 100 parts at 350 to 10 to 25
Cellulose dope as described above, characterized in that after being kept at 0 atm, the cellulose rapidly released into the atmosphere is mixed with an alkaline aqueous solution adjusted to 50 ° C. or less in advance and stirred and dissolved at 10 ° C. or less. To provide a manufacturing method of.

The cellulose dope of the present invention is stable and contains cellulose in a high concentration, and is suitable for molding. That is, the cellulose dope of the present invention has a degree of polymerization of at least 10.
It is an alkaline aqueous solution dope of cellulose containing 3% by weight of 0 or more cellulose, and is stable at room temperature without gelation for 2 days or more. The greatest feature of the present doped, the carbon C ₄ position of the glucose rings constituting cellulose ¹³
The C-NMR peak is derived from the strong intramolecular hydrogen bond existing in the crystal part of solid cellulose. C ₄ peak (89.1 ppm for cellulose I, 89.1 ppm for cellulose II and 87.9 pp)
m) is found in a magnetic field higher than 7 ppm. Cellulose solids generally consist of crystalline and amorphous parts, which are C ₄ due to intermolecular and intramolecular hydrogen bonding.
¹³ C-NMR of carbon at position is observed as the above-mentioned peak and a broad peak extending from 86 to 79 ppm due to the difference in crystal system (see FIGS. 1A and 1B. Both figures show natural cellulose and regenerated cellulose, respectively). Solid CP /
Represents a MAS ¹³ C-NMR spectrum. ). The latter peak is considered to be a superposition of various peaks mainly depending on the degree of destruction of intramolecular hydrogen bonding. Although ordinary cellulose to swell in an alkali, the swollen cellulose solution, ¹³ C-NM
In the R spectrum, the C ₄ carbon is broad and is not found as a single sharp peak in a magnetic field higher than 7 ppm based on the above-mentioned 89.1 ppm peak. In the alkaline solution of cellulose of the present invention, it is observed as a single sharp peak in a high magnetic field of 7 ppm or more (see FIG. 2).

Furthermore, the cellulose in the solution exhibits a completely different dissolution state from the cellulose in the copper amonia solution or viscose conventionally used industrially in that no specific coordination of alkali is observed, and the so-called Does not require a replay operation.

The degree of polymerization of cellulose constituting the dope of the present invention is 100.
Above, it is preferably 200 to 700. If it exceeds 700, there is a slight problem in the molding operation in that it is highly viscous and easily gels. However, this problem can be solved by performing the molding operation immediately after preparing the solution using an apparatus such as an extruder, so the upper limit is extremely limited. Not relevant.

The cellulose dope of the present invention is prepared by pre-treating cellulose having various crystal forms to obtain C ₃ -O ₅ ′ (between OH at the C ₃ position and ring oxygen), C ₂ -C ₆ (C ₂ OH and C ₆ O or between C ₂ O and C ₆ ′ OH) having a low intramolecular hydrogen bonding property and obtained by dissolving it in an alkaline aqueous solution at a low temperature. Cellulose necessary for producing the dope of the present invention, for example,
A mixture of cellulose I crystal type (natural cellulose), cellulose II, III, IV crystal type (regenerated cellulose) and a hydrogen bond cleaving agent is added at 100 to 350 ° C.
It is obtained by maintaining the pressure at 10 to 250 atmospheres and then rapidly releasing it at room temperature and in the atmosphere.

Temperature and pressure correlate to each other, resulting in the vapor pressure at a particular temperature of the vaporizable components present in the hydrogen bond cleaving agent. Therefore, the temperature must be below the thermal decomposition point (350 ° C.) of cellulose. Further, in consideration of reuse of volatile components other than water, it is desirable to operate below the decomposition point of the component. Also, for example, when external pressure other than the vapor pressure of steam is applied by an extruder, etc., depending on the external pressure,
It is desirable to adjust the treatment temperature so that it is raised appropriately.
The time for holding the cellulose in the atmosphere is not limited, and may be determined according to the thermal alteration and thermal decomposition of the cellulose. About 20 seconds to 20 minutes is usually sufficient.

The amount of the component capable of evaporating in the hydrogen bond cleaving agent is appropriately 10 to 100% by weight based on cellulose. When the amount of the component that can be evaporated is less than 10% by weight, when the mixture of the cellulose and the hydrogen bond cleaving agent is released into the atmosphere from a high temperature and high pressure state, the cellulose by the rapid evaporation of the liquid constituting the hydrogen bond cleaving agent is used. Internal destruction (intramolecular hydrogen bond destruction)
Is insufficient, and alkali solubility at low temperature is insufficient. Ten
If it exceeds 00% by weight, the cost becomes energetically high.
As the hydrogen bond cleaving agent, water, alkaline aqueous solution, inorganic acid aqueous solution, salt aqueous solution, urea aqueous solution, aqueous solution or aqueous dispersion of amphoteric oxide or amphoteric hydroxide, glycols, amides, sulfoxides, halogenated Acetic acid, polyphenol, etc. are used. Of course, a mixture of these can also be used. Among the hydrogen bond cleaving agents, those described as an aqueous solution or a hydrous acid solution can achieve the same effect even when the solute or dispersoid is supplied in a solid state to cellulose moistened with water. The ratio of the solute or dispersoid component to water to be supplied to the cellulose is not limited, and the upper limit is the saturated solubility range of the solute or dispersoid component in water. In general, 1 to 3 equivalents of these components are sufficient, assuming that all the cellulose molecular chains to be treated are completely intramolecularly hydrogen-bonded (1 / glucose residue). Addition beyond that is economically disadvantageous.
However, when the aqueous solution is acidic, if the PH is too high, the cellulose will be depolymerized more than necessary, and therefore it is appropriately adjusted depending on the acid species used. Generally, in an aqueous solution exhibiting acidity, 1
It is desirable to supply at a concentration of 0% by weight or less. Of course,
Since the dope of the present invention is a solution in which the cellulose treated as described above is dissolved in an alkali, it is economically disadvantageous to use an excessively acidic aqueous solution in the cellulose treatment step also in this sense. . In addition, it is absolutely necessary to use a small amount of oxidizing substances such as nitric acid and perchloric acid as low as possible. As the alkaline aqueous solution in the hydrogen bond cleaving agent, an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, beryllium hydroxide, calcium oxide, sodium silicate, sodium carbonate, tetraalkylammonium or the like is preferable. The aqueous solution of inorganic acid is preferably an aqueous solution of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, perchloric acid, hypochlorous acid, chlorous acid, nitrous acid, sulfurous acid, boric acid, or the like. As a salt solution,
Aqueous solutions of lithium chloride, zinc chloride, calcium thiocyanate, ammonium thiocyanate, sodium thiocyanate and the like are preferred. As the amphoteric oxide and hydroxide, oxides and hydroxides such as aluminum and zinc are preferably used.

The above-mentioned treatment of cellulose can be carried out batchwise or continuously. In the case of a batch method, a mixture of cellulose and a hydrogen bond cleaving agent is placed in a pressure resistant container, and 100 to 350
After externally heating the mixture and letting it stand in the vapor pressure atmosphere of the vaporized components in the mixture for a few seconds to a few minutes, in order to rapidly reduce the pressure inside the pressure vessel, open the valve and nozzle attached to the vessel in advance and release the cellulose. It is obtained by The obtained cellulose is washed with water as needed, dried, and then subjected to a dissolving step. In the case of the continuous type, the above mixture is supplied to an externally heated single-screw or twin-screw extruder, and the mixture pressurized by the vapor pressure of the vaporized components in the mixture and the extruder pitch is introduced from the tip of the extruder. Obtained by releasing. In this case, external heating can be set for each zone. Further, the cellulose and the hydrogen bond cleaving agent can be mixed in the extruder. That is, while feeding the cellulose with a feed screw, pressure feeding may be performed from an opening provided on the side of the extruder. The screw may be any combination of a feed screw, a reverse screw and a seal screw. The degree of polymerization of the cellulose thus obtained can be adjusted in advance with an acid or an alkali before the treatment, or can be adjusted during the above operation. In any case, it is adjusted to 100 or more. The cellulose / hydrogen bond cleaving agent mixture thus treated is finally dried by removing unnecessary components by washing with water. However, the components in the hydrogen bond cleaving agent that do not hinder the solubility of cellulose may be mixed together in the end. Such a component is basically a substance that does not exhibit acidity.

Effect of the Invention The dope of the present invention is prepared by dissolving a specific cellulose having a relatively high degree of polymerization in an alkaline aqueous solution at a low temperature. In this dope, since cellulose is dissolved in the state without intramolecular hydrogen bonding as described above, and in the state without coordination to the specific glucose ring of alkali, the cellulose conventionally used industrially. It has a completely different dissolution state from the solution (copper ammonia solution, viscose solution). Therefore, the cellulose molded product obtained from this dope also has characteristics different from the conventional ones. The dope can be molded into a fibrous or film-like shape by neutralizing the solution by extruding the solution from a spinning hole or a slit using an ordinary extruder and then solidifying and stretching the solution. The coating can be formed by coating the surface or the inside of another material, or by immersing the other material in the dope.

Since cellulose is completely molecularly dispersed in the dope of the present invention, when it is returned to a cellulose solid by neutralization, it tends to have a more complete higher-order structure. The most characteristic feature of the cellulose molded article obtained from this dope is that it has a high intramolecular hydrogen bonding property as compared with conventional regenerated cellulose fibers and membranes. The intramolecular hydrogen bondability can be evaluated by infrared absorption or NMR. As described above, since the obtained molded product has a high intramolecular bonding property, it has excellent mechanical properties and chemical resistance.

Examples Hereinafter, the present invention will be described with reference to Examples.

Example 1 This example discloses an example of directly producing alkali-soluble cellulose from natural cellulose (Cellulose I crystal type) by using a biaxial extruder type high temperature and high pressure apparatus.

As the natural cellulose, Saika pulp (average degree of polymerization 910) made of eucalyptus and acid hydrolyzate depolymerized pulp (average degree of polymerization 580) for depolymerization were used. On the other hand, as a twin screw extruder type high temperature and high pressure apparatus, α-100 type manufactured by Suehiro Iron Works was used. The main specifications of the device are a processing capacity of 50 to 100 Kg / H, a screw rotation speed of 65 to 260 rpm, and a temperature control range of water temperature to 300.
℃, withstand pressure less than 200Kg / cm ² , screw diameter 80mmφ,
The screw length is 640 mm (one screw is composed of five screw units), and in this embodiment, the feed screw (I) (pitch 50 mm), the seal screw, the feed screw (II) (pitch 35 mm), the feed screw (III ) (Pitch 30 mm) and reverse screw (pitch 20 mm). A die having a diameter of 10 mmφ was used for the discharge port of the object to be treated. The temperature was set to 150 ° C. excluding the feed screw (I) and the seal screw part, and the temperature was measured at three points: the die part, the reverse screw part, and the feed screw (III). The pressure was measured at two locations, the die section and the reverse screw section. However, this pressure is a shear pressure, not the vapor pressure of the transpiration component in the hydrogen bond cleaving agent. The screw rotation speed was set to 120 rpm. In the actual treatment, the cellulose is immersed and stirred in 20 times (weight) water to form a slurry, which is then dehydrated to 1 weight of the cellulose,
A mixture with 3 parts by weight of water was used as a hydrogen bond cleaving agent, and this was fed to the pretreatment unit at a rate of 20 kg per hour.

The pressure during the treatment of Saika pulp and its acid hydrolyzate was 20 to 50 kg / cm ² . The treated cellulose was a white powder and contained several tens% of water. The powdery cellulose was vacuum dried at 40 ° C. for 24 hours and evaluated for alkali solubility. When the viscosities in cadoxene were determined, the polymerization degrees were 760 and 420, respectively. 9.1 wt% sodium hydroxide aqueous solution for alkali, Henschel type dissolver (volume 5), dissolution temperature 5
As a result of being dissolved under conditions of ± 5 ° C., dissolution concentration of 6.5% by weight, dissolution time of 2 hours, etc., a viscous, transparent and glossy solution was obtained along with the above-mentioned cyca pulp and acid hydrolyzate. Was given. Take a portion of this solution, add a little heavy water, and use it as the lock signal, based on TSP
¹³ C-NMR was measured. The results are shown in FIG. Apparently, C ₄ carbon was observed as one sharp peak at 79.95 ppm. As a result of observing the dissolved state with an optical microscope (under crossed Nicols), in the case of syca pulp, a slight amount of undissolved fiber was observed, but it was sufficiently removable by filtration with a filter press or the like. On the other hand, in the case of the treated acid hydrolyzate, no undissolved particles were observed, and it was confirmed that an extremely uniform solution was formed. It was stable at room temperature for 3-5 days.

On the other hand, when the above-mentioned untreated cellulose was dissolved under the same conditions, it appeared as a cloudy solution at first glance and had a low viscosity, and the entire visual field of the optical microscope (under crossed Nicols) was almost unclear. It was almost impossible to give a visual field and remove this undissolved portion with a filter press or the like. When this solution was measured by solid-state NMR, there was a sharp peak at 80 ppm, but quite large peaks were also present at 87.8 ppm and 85 to 82 ppm.

Among the above-mentioned conditions of the examples, the weight of water as a hydrogen bond cleaving agent was set to 0.1 part by weight per 1 part by weight of cellulose, and the acid-hydrolyzed saicore pulp was treated under the above operating conditions. Although it was obtained as a solid, the degree of polymerization was 580 to 320, and when it was dissolved by the above-mentioned dissolution operation, the solubility was improved as compared with untreated pulp, but optically significant undissolved material was present. It was approved to do.

Example 2 Using the twin screw extruder described in Example 1, the hydrogen bond cleaving agent described in Table 1 was mixed with cellulose at various ratios under the same conditions, and unnecessary components were removed after the treatment. Cellulose concentration was set to 6.5% for two cases, that is, the case and the case where it was not removed, and dissolution was performed under the conditions described in Example 1. The results are shown in Table 1. In the table, ◯ indicates the dope of the present invention, Δ indicates that the undissolved substance is about 10%, which is considerably improved compared to the untreated, and x indicates the dope which is not much different from the untreated. The raw material cellulose for processing in this example is Alaska pulp (A (DP = 75
0)), cotton linter (B (DP = 1100)), regenerated fiber (C (DP = 55)
0)).

As is clear from Table 1, various hydrogen bond cleaving agents can be used to produce the dope of the present invention. Also, Table 1
It should be noted that the material remaining in the treated cellulose may be disadvantageous in dissolving the treated cellulose in alkali, as will be seen more clearly. ○ in the table
The ¹³ C-NMR spectrum of the dope of the present invention marked with, C ₄
All carbon was observed as a single sharp peak at 80-79 ppm.

Example 3 In this example, a method of treating cellulose by a so-called explosion method, in which a mixture of cellulose and water is kept under high temperature and high pressure for a short time and then rapidly released into the atmosphere, In addition, a method for preparing a dope composed of the cellulose and an aqueous alkaline solution will be exemplified.

For natural cellulose, wood pulse 60% with 5N sulfuric acid
What was treated at 90 ° C. for 90 minutes was used. The cellulose is
It had a degree of polymerization of about 600 due to the viscosity in cadoxene. 500 g of this cellulose was immersed and stirred in 5 of water to form a slurry-like mixture, and this mixture was put into an 18 autoclave. Silicone oil heated to 270 ° C. was poured into the autoclave jacket, and 5 minutes after the temperature inside the autoclave reached 250 ° C., the pressure reducing valve was rapidly opened to reduce the pressure. Cellulose obtained by pouring 4650 g of a 9 wt% caustic soda aqueous solution into a Henschel dissolver with a jacket controlled at 20 ° C. and stirring
0 g was added slowly. 30 minutes after the addition, the jacket temperature was cooled to 110 ° C. and stirring was continued for 3 hours. As a result of observing the obtained solution with an optical microscope (under crossed Nicols), almost no undissolved particles were observed.

Similarly, in an autoclave preheated to 230 ° C., 12.5% by weight of water was previously added to decompose water of oxidation with a degree of polymerization of about 400 (treated for 180 minutes in the same manner as described in this Example). Stuff) Pulp, 23
Steam at 0 atm was bubbled in until the vapor pressure was constant, sealed and held for 8 minutes. As in the previous case, the pressure reducing valve was rapidly opened to reduce the pressure. The resulting cellulose dissolved equally well in the same manner as before.

Further, when the above solution was diluted with 9 wt% of deuterated caustic soda solution to a cellulose concentration of 5 wt% and the ¹³ C-NMR spectrum was measured, the same spectrum as in FIG. 2 was obtained.

On the other hand, a film obtained by casting the solution on a glass plate using a 500 μm knife coater, coagulating a 10 wt% sodium sulfate aqueous solution, washing with 2 wt% sulfuric acid, washing with water, and drying is transparent. It had a feeling and was practically durable.

Example 4 This example discloses dopes dissolved in various concentrations of alkali using the acid hydrolyzed syca pulp treated in Example 1. Table 2 shows the dissolution conditions, dope properties, and stability. A Henschel type mixer was used for dissolution.

[Brief description of drawings]

FIGS. 1A and 1B show solid-state CP / MAS ¹³ C-NMR spectra of natural cellulose and regenerated cellulose, respectively, and the peak of the arrow shows the carbon peak at the C ₄ position based on a strong intramolecular hydrogen bond. FIG. 2 shows the ¹³ C-NMR spectrum of the dope solution of the present invention, in which the C ₄ position is observed as a single peak.

Claims (2)

[Claims] 1. A degree of polymerization of more than 100 cellulose be substantially 3 of cellulose containing wt% or more alkali aqueous solution doped, in its ¹³ C-NMR spectrum, C
_A cellulose dope suitable for molding, wherein the carbon peak at the _4- position is found in a magnetic field higher by 7 ppm or more as compared with the carbon peak at the C4-position based on a strong intramolecular hydrogen bond. 2. A mixture consisting of 100 parts by weight of cellulose having an arbitrary crystal form and 10 to 1000 parts of a hydrogen bond cleaving solution is maintained at 100 to 350 ° C. under 10 to 250 atm, and then rapidly released into the atmosphere. Then, the obtained cellulose is mixed with an alkaline aqueous solution adjusted to 50 ° C. or less in advance, and stirred and dissolved at 10 ° C. or less to dissolve the cellulose dope.